Diablo Valley College Lecture 1 to 5 SI Base and Derived Units Worksheet

What topics should you include?

From Lectures 1-5 and Learning Outcomes 1-18, here is a list of concepts that you should endeavor to include on your Concept Map #1 (Note: You may add others, if you wish).

• Scientific Process
• Measurement; SI Base and Derived Units
• Hypothesis
• Theory
• Law
• Physical States (gas, liquid, solid)
• Elements
• Compounds
• Mixtures
• Physical Property (examples)
• Chemical Property (examples)
• Physical Change (examples)
• Chemical Change
• Law of Conservation of Mass
• Atomic Theory
• Law of Constant Composition
• Law of Multiple Proportions
• Atomic Models – Dalton (Billiard Ball), Thompson (Plum Pudding), Rutherford (Nuclear)
• Protons, Neutrons, Electrons
• Atomic Symbol
• Mass Number, Atomic Number
• Isotopes
• Ions
• Relate Atomic Mass
• AMU
• Periodic Table
• Group, Period
• Main Group Elements, Transition Elements, Inner Transition Elements
• Metals, Metalloids, Semi-Metals
• Alkali Metals, Alkaline Earth Metals, Chalcogens, Halogens, Noble Gases

How should you build your map?

You’ll want to create a draft, where you are connecting the nodes (concepts above) to each other. Try out different arrangements of major and minor topics. [You could write the terms on scrap pieces of paper and move them about until you’re happy with the orders and connections you’ve made.]. After you have the concepts arranged, you’ll want to link the nodes and brainstorm about the connecting words/phrases that you’ll include between nodes. You’ll also want to look for cross-links, which will appear between different parts of your map.

Remember: You can do this exercise either on paper, or with tools such as word processing and documentation tools (like Word) or drawing programs.

You can include images (diagrams, plots, etc.) and equations, especially if they help convey the meaning of the concept.

Here is an Example of a Concept Map that highlights aspects of Measurements (Note that there are no cross-links featured):

Something to think about: What would you add? change? Notice the linking terms/phrases in blue. These are important. What do you think the color code is trying to convey?

Here is an Example of a Concept Map that highlights key concepts associated with Free Energy (Note again that there are no cross-links featured):

University of California San Diego
CHEM 6A: Concept Map Assessment
GOAL: This exercise is intended to give you an opportunity to demonstrate the comprehensive
knowledge and understanding you are developing this quarter in General Chemistry 6A. As an
assessment format, a concept map promotes independent reflection, allows for creativity, and
alleviates the potential stress of a timed quiz/exam. Further, it serves as a great study tool! As you
review, you remind yourself of connecting concepts by building your map (and you can earn course
credit in the process!).
What is a concept map?
A concept map is a visual graphic that represents how an individual thinks about a subject, the
hierarchies and interconnections of concepts. It is divided into nodes (boxes/circles for the various
concepts) and links (lines) that show the relationships (propositions) between concepts, with linking
terms (typically a verb) to explicitly describe the relationship.
proposition = 2 concepts + linking description
Image credit: FLAG
Chemistry 6A (© Brydges)
University of California San Diego
How do you create a concept map of CHEM 6A (as part of our Bi-weekly Learning
Checks)?
1. Start by writing a list of key terms for each main topic. (Hint: Look back at the Learning
Outcomes, and the bolded terms from your Lecture Notes, Discussion Guides, etc.)
2. Arrange concepts (words, images, mathematical equations, plots, etc.) in a hierarchical
format, starting with the most general topic(s) at the topic. The map will become more
specific as you move downwards/outwards.
3. Connect ideas as you go. That is, draw an arrow or line between related concepts.
Alongside the arrow, define the relationship using a verb or phrase that links them.
4. Where possible, create cross-links between concepts in different domains of the concept
map.
5. Check and revise as needed.
• Have key vocabulary terms been effectively integrated?
• Have you explained concepts/relationships in your words or phrases?
• Are the connections between ideas logical and accurate?
•
•
Are the link labels correct and precise?
Does the quantity and complexity of the map nodes reflect deep understanding?
For a simple example, this video is helpful: https://www.youtube.com/watch?v=8XGQGhli0I0
Note: We am not promoting the tool, though you may wish to use it or another free, online concept
map maker (please share ideas on Canvas discussion board). You can use word, or sketch your map
by hand (on paper or an electronic device) – Whatever is easiest and most convenient for you. It is
the content and clarity of presentation that is most important.
You are welcome to share and receive comments on your concept map with and by your peers, but
you must develop and submit YOUR original work – this is YOUR study tool! No two concept maps
should ever look the same – because no two people have the same way of seeing and representing
the (chemistry) world. [In technical terms, we’d say that everyone has different cognitive structures.]
Deadline: Each Friday of Scheduled Learning Check, by 11 PM.
Submission Format: Please upload a PDF version of your final document to the Canvas assignment.
Questions? Please contact Dr. Brydges and/or your Graduate TA.
Chemistry 6A (© Brydges)
University of California San Diego
Grading Rubric: ___ /15 points (for 2.5% of overall grade)
Performance
Level 1 (1 pt)
Level 2 (2 pts)
Level 3 (3 pts)
Indicators
Concepts
(Use of Nodes)
Hierarchical
Structure
Direct
Linkages
Insufficient number of
concepts relating to each
topic included.
Minimal but acceptable
number of concepts
included.
All significant concepts
related to each topic are
included.
Little or no generalintermediate-specific
structure used. i.e. map
has unclear hierarchies.
Lines connect concepts;
linking words and phrases
are simple and/or
repetitive and/or missing
Some hierarchical structure
is used.
Concepts are connected
from general to increasingly
specific. i.e. map has
multiple, clear hierarchies.
All relationships are
indicated by a connecting
line; linking words or
phrases are accurate and
varied.
Cross-links
Cross links are not used.
Overall
Arrangement of concepts
does not indicate an
understanding of
conceptual relationships
Layout
Map is poorly laid out,
confusing to read.
Most (if not all)
relationships are indicated
by a connecting line;
linking words or phrases
show variety but contain
some inaccuracies.
Some cross links are used
to represent
straightforward
connections.
Arrangement of concepts
demonstrates a correct but
not fully developed
understanding of
conceptual relationships.
Map is fairly well laid out.
Chemistry 6A (© Brydges)
Cross links show complex
relationships between two
or more distinct segments
on the concept map (i.e.
major/minor topics in the
course).
Arrangement of concepts
indicates a comprehensive
understanding of
conceptual relationships.
Map is well laid-out.
General Chemistry 6A
(Early) Atomic Models to the Periodic
Table
Fundamentals & Focus 1
Fundamental B and Topic 1A.1
What are the early atomic models? What distinguishes atoms of
different elements? How is the periodic table arranged?
Atomic Theory
CHEM 6A
The Nuclear Atom
The Periodic Table
& Chemical Periodicity
2
Atoms & The Periodic Table
Your Learning Goals
Can you …
•
Apply the Law of Constant Composition and the
Law of Multiple Proportions.
•
Outline Dalton’s Atomic Theory of Matter, and its
shortcomings.
•
Describe the nuclear atom and the experiments that
led to the discovery of subatomic particles.
•
State the number of protons, neutrons, and
electrons in particular atoms and ions (as well as
the mass number, A and the atomic number, Z).
CHEM 6A
I don’t get it!
I need to re-read,
practice problems,
and seek help.
I kind of get it!
I need to re-read
for clarification,
practice problems,
and seek help if I
have questions.
I got it!
I need to engage in
deliberate practice
to reinforce my
understanding.
I got it! I can teach
it to a friend.
I still need to
practice from time to
time (for retention).
3
Atoms & The Periodic Table
Your Learning Goals
Can you …
•
•
•
Calculate the relative atomic mass of an element
(given the percent natural abundances of its stable
(i.e. non-radioactive) isotopes) expressed in
atomic mass units.
Recognize the patterns of chemical reactivity
associated with the chemical elements of the main
group, and thus the general format of the periodic
table.
Classify the chemical elements as metals,
metalloids, or non-metals, by their physical states
(solids, liquids, and gases) at STP, and by their
occurrence, origin, and form on Earth.
CHEM 6A
I don’t get it!
I need to re-read,
practice problems,
and seek help.
I kind of get it!
I need to re-read
for clarification,
practice problems,
and seek help if I
have questions.
I got it!
I need to engage in
deliberate practice
to reinforce my
understanding.
I got it! I can teach
it to a friend.
I still need to
practice from time to
time (for retention).
4
Atomic Theory:
When and How Did We Gain Insight into
the Microscopic World of the Atom?
(“From Caveman to Chemist”, by Hugh W. Salzmann)
CHEM 6A
5
Models of the Atom
As details of its sub-structure were discovered, the model of the
atom has been revised over the last two centuries:
“Billiard ball” “Plum pudding” “Planetary”
model
model
model
1803
1897
1911
“Bohr”
model
1913
“Quantum
mechanical” model
1923 – 1926
Today, the quantum mechanical model provides the most
accurate description of the atom.
CHEM 6A
6
Points to Ponder
What is a scientific model?
produced? tested? refined?
CHEM 6A
What is its purpose? How is it
7
A “Matter” of Time …
5000 B.C.: Troy, etc. … chalks, glass, pigments, textiles, tea
ca. 460-370 B.C.: Democritus’ atomos º indivisible
ca. 50 B.C.: Lucretius “DE RERUM NATURA” (On the Nature of Things)
“All nature consists of twain of things: of atoms and
of the void in which they’re set.”: In other words,
all matter consists of tiny fundamental building
blocks, atoms.
0 B.C.: Greece, Rome – Ancient Alchemy … “air, earth, fire and water”
… medicinal ointments, plant-based medicine
1000: Medieval Europe, Arabic Alchemists … gunpowder, soap and more
CHEM 6A
8
A “Matter” of Time …
1700-1800:
Age of Enlightenment … strong acids, alcohols,
microscope, telescope, steam engine, …
Joseph Wright of Derby’s “The
Alchymist, In Search of the
Philosopher’s Stone, Discovers
Phosphorus.” (1771)
CHEM 6A
Chemistry symbols describing alloys,
compounds, chemical operations, etc.
in the 18th century “L’Encylopedia” by
Diderot and D’Alembert
9
The Birth of Modern Chemistry:
Who Took the Intellectual Leap?
1775
1794
1803-8
Antoine Lavoisier
Joseph Proust
John Dalton
The Law of
Conservation of Mass
The Law of
Constant Composition
Atomic Theory of
Matter
http://www.chemheritage.org/explore/explore.html
CHEM 6A
10
Quantitative Analysis à Experimental Data
Late 1700s: Lavoisier and Proust
Law of Constant Composition
Two samples of a given compound are made of the same elements in the
same proportions, no matter their source.
Example: NaCl is always 60.66% chlorine and 39.34% sodium by
mass. So, a 1.00 g sample will contain 0.6066 g Cl and 0.3934 g Na.
Law of Multiple Proportions
Multiple compounds can be made from the same two elements. The
masses of one element which combine with a fixed mass of the second
element are in a ratio of whole numbers.
Example:
compound 1: 16 g of O reacts with 14 g of N
compound 2: 16 g of O reacts with 28 g of N
28/14 = 2 à a small whole number
CHEM 6A
11
Polling Q: Law of Multiple Proportions
Which set of compounds is NOT represented by the data below?
(A) NO and N2O
(B) NO2 and N2O2
(C) NO and NO2
Example:
CHEM 6A
compound 1: 16 g of O reacts with 14 g of N
compound 2: 16 g of O reacts with 28 g of N
12
The Atomic Theory
Early 1800s: Dalton
In John Dalton’s “A New System of Chemical Philosophy” (1808),
the evidence for the existence of atoms is marshaled:
1.
2.
3.
4.
All matter consists of extremely small, indivisible particles called atoms.
All atoms of a given element are identical in mass and other properties.
Different chemical elements have different kinds of atoms; in particular, their
atoms have different masses.
A chemical reaction involves a rearrangement of atoms; no atoms are
created, destroyed, or broken apart (Law of Conservation of Mass).
And later …
5.
6.
Compounds are formed when atoms of different elements unite in fixed
proportions (Law of Definite Proportions).
Deduction: More than one compound can be formed from the combination of
two elements; this implies a Law of Multiple Proportions.
CHEM 6A
13
The Atomic Theory
Early 1800s: Dalton
The spheres that Dalton used to demonstrate atomic theory.
Image: Manchester Museum of Science & Industry/SSPL
CHEM 6A
14
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
15
What is the Nuclear (Rutherford)
Model of the Atom?
CHEM 6A
16
The Physical Structure of the Atom:
Is it Really Indivisible?
• Dalton’s Atomic Theory was derived from evidence obtained
at the macroscopic level
However …
• Development of instrumentation capable of probing
phenomena at a microscopic level has given us further
understanding of the atom
CHEM 6A
17
The Discovery of Electrons
1897: J.J. Thompson (Cathode Rays)
Cathode rays, or
“current carriers”,
are emitted when a
high potential
difference is applied
between two
electrodes.
Material particles of NEGATIVE charge and unknown mass; The
ratio of the charge to mass (e/me) of the electron are measured.
CHEM 6A
18
Early Atomic Models
1904: Thomson Model of the Atom: A Plum Pudding?
Hypothesis: Neutrality is
provided by a nebulous
cloud of positive charge
CHEM 6A
19
The Discovery of Electrons
1906-14: Robert Millikan (Oil Drop Experiment)
Adjust electric field to
balance two forces:
-Mg = QE
Charge Q is always an
integral multiple of ~
1.6 x 10-19 C.
The charge of the electron, e, (and its mass, me) are determined.
Late 1800s-early 1900s: Many new insights and spin-offs: radiation
CHEM 6A
20
A Detailed Model of the Atom Emerges
1909-1911: Ernest Rutherford (Metal Foil Experiment)
Alpha (a) particle = helium nucleus
(positively charged)
LARGE
deflections
of
alpha-particles
observed: “It was almost as incredible as if
you fired a 15-inch shell at a piece of tissue
paper and it came back and hit you.”
Provides estimation of the atomic radius and identifies positive
charge at center of atom (“nucleus”).
CHEM 6A
21
What Makes Up the Nucleus?
1920: Ernest Rutherford
• Hydrogen atom is the fundamental unit of positive charge, +e
• Proposed the term “proton”: different elements have different
numbers of protons in the nucleus of the atom
1932: James Chadwick
• Discovered the “neutron”, which has mass but no charge
• Role in stability: prevents electrostatic repulsions between
protons and the dissociation of the nucleus
CHEM 6A
22
Nuclear Model of the Atom
Atoms, which are electrically neutral, are made of three subatomic particles: protons (p), electrons (e-) and neutrons (n).
uncharged
positively charged
(+e)
negatively charged
(-e)
CHEM 6A
23
Nuclear Model of the Atom
Electrons have a mass that 1/1836 times that of a proton or a
neutron! We’ll see shortly how we express the absolute mass
(kg or g) in terms of a relative mass (amu).
CHEM 6A
24
Nuclear Model of the Atom
The elementary charge (e) is 1.602 x 10-19 C (Coulombs).
In atomic (or relative) units, the electron is assigned a charge of -1,
and the proton is assigned a charge of +1. The charges are equal
in magnitude but opposite in sign.
CHEM 6A
25
Nuclear Model of the Atom
The nucleus is at the center of the atom and contains the protons
and neutrons. The electrons move rapidly through a large, mostly
empty volume of space about the nucleus.
Charge on nucleus is +Ze,
where Z = number of protons.
It follows that Z electrons
must surround the nucleus.
Since electrons “weigh” so little, virtually all the mass of an atom
is concentrated in the nucleus.
CHEM 6A
26
Nuclear Model of the Atom
Measurements show that the diameter of a nucleus is about 10-15
m, whereas the atom itself is about 10-10 m wide.*
* These values depend on the element.
CHEM 6A
27
Atomic Structure
In Perspective
If an atom was the diameter of our 1200 acre (4.85 x 106 m2) campus,
the nucleus would be about the size of a U.S. quarter (25 mm).
CHEM 6A
28
Atomic Structure
In Perspective
Approximately how many atoms can you line up across the
widest part of a pinhead that measures 1 mm in diameter?
1 atom
10 −10 m
1m
1 mm
7 atoms
× 3
×
= 10
or 10 million atoms!!!
10 mm
pinhead
pinhead
Figure from: http://www.nclt.us/grg/23011.pdf
CHEM 6A
29
Atomic Structure
What is the “Glue” Holding Together the Atom?
The structure of an atom is determined by an interplay of
different forces.
• Electrostatic (Coulombic) forces keep electrons apart
(repulsion of like charges) but draw them to the protons in the
nucleus (attraction of opposite charges).
• Protons in the nucleus are held together by a strong nuclear
force, one of the 4 known forces in the universe.
CHEM 6A
30
Are You Wondering?
A study of matter at its most fundamental level must consider
many additional subatomic particles (beyond neutrons, protons,
and electrons). This is the subject of elementary particle physics,
rather than chemistry.
If you’re wondering about quarks, leptons, and
bosons, watch the video titled CERN, the
European Organization for Nuclear Research:

CHEM 6A
31
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
32
So What Makes Atoms of One Element
Different from Another?
A
E
Z
CHEM 6A
33
Atoms of an Element
Number of Protons (Atomic Number, Z)
ALL atoms of a given element possess the same number of
protons (p) in their nuclei. This value is unique to each element
and is called its atomic number (Z).
Examples:
1p
6p
8p
hydrogen
Z=1
carbon
Z=6
oxygen
Z=8
That is, if an atom has 1 proton, then its atomic number is 1, and it is
hydrogen. If an atom is hydrogen, it has 1 proton.
CHEM 6A
34
Atoms of an Element
Number of Electrons
Since an atom is electrically neutral, it follows that:
number of electrons = number of protons (Z)
Examples:
€
1p
1e-
hydrogen
Z=1
6p
6e-
carbon
Z=6
8p
8e-
oxygen
Z=8
So, if a carbon atom (Z = 6) has 6 protons, it must also have 6 electrons
surrounding its nucleus, and so on.
CHEM 6A
35
Atoms of an Element
Number of Neutrons (N)
The number of neutrons (N) in an atom of a given element may
vary.* Except for hydrogen, N is always equal to or greater than
the number of protons in the nucleus.
Examples:
1p
1e-
6p
6n
6e-
8p
8n
8e-
hydrogen
Z=1
carbon
Z=6
oxygen
Z=8
N=0
N=6
N=8
* There is no simple way to predict how many neutrons a given atom will
have.
CHEM 6A
36
Atoms of an Element
Mass Number, A = N + Z
Electrons have negligible mass, so it is the total number of protons
and neutrons in the nucleus of the atom that define its mass
number (A).
Examples:
CHEM 6A
1p
1e-
6p
6n
6e-
8p
8n
8e-
hydrogen
Z=1
carbon
Z=6
oxygen
Z=8
N=0
A=1
N=6
A = 12
N=8
A = 16
37
Atoms of an Element
Common Notations
In representing the composition of an atom, the atomic number and
mass number are often included with the atomic symbol:
A
Z
E
E = Chemical symbol of an element
A = Mass Number = p + n
Z = Atomic Number = p
A
E
In a different notation, the chemical symbol (or chemical name) is
followed by a dash and the mass number.
E-A
CHEM 6A
Element Name-A
38
Atoms of an Element
Common Notations
We can apply these notations to our previous examples:
Examples:
1p
1
1
H or 1H
hydrogen-1
H-1
€
€
6p
6n
1e
12
6
8p
8n
6e
C or 12C
carbon-12
C-12
16
8
8e
O or 16O
oxygen-16
O-16
€
The mass number, A, is important for distinguishing isotopes.
CHEM 6A
39
Polling Q: Atomic Symbols
An atom of uranium-235 (Z = 92) has how many protons
(p), electrons (e-), and neutrons (n) ?
(A) 92 p, 92 e-, 143 n
(B) 92 p, 43 e-, 235 n
(C) 92 p, 92 e-, 235 n
(D) 235 p, 235 e-, 143 n
CHEM 6A
40
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
41
What is the Difference Between an
Isotope and an Ion?
A
E
Z
CHEM 6A
42
Atoms of an Element
Different Neutron Counts: ISOTOPES
Isotopes are atoms of an element that have different numbers of
neutrons (N), and thus, different mass numbers (A).
Example: A sample of hydrogen atoms consists of …
1
1
1
H (hydrogen)
99.985%
!
These atoms
possess
!
(because of e- counts).
1
2
1
H (deuterium)
0.015%
nearly
identical
!
1
3
1
H (tritium)
0% (synthesized in nuclear reactor)
chemical
properties
Dalton’s postulate was incorrect: Atoms of a given element may not be identical in mass!
CHEM 6A
43
Atoms of an Element
Different Electron Counts: IONS
A (monatomic) ion is a charged particle formed when a neutral
atom loses or gains one or more electrons.
CATION: a positively charged ion.
ANION: a negatively charged ion.
The symbol for an ion is written by adding the electrical charge as
a superscript to the right of the symbol for the element.
Example: Na ® Na+ + e11p 10e12n
CHEM 6A
Example: Cl + e- ® Cl−
17p 18e18n
44
Class Problem
24
25
24
16
CHEM 6A
Mg
Mg
Mg2+
O2-
# of protons
# of electrons
# of neutrons
12
12
12
?
12
13
?
?
?
?
?
?
A
E
Z
45
Polling Q: Electrons and Protons
In which of the following sets do all species have the same
number of electrons (i.e., are isoelectronic)?
(A) K+, Rb+, Cs+
(B) Cl-, Ar, Ca2+
(C) Br, Br-, Br+
(D) C, N3-, O2-
CHEM 6A
46
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
47
How Do We Calculate Atomic Mass?
CHEM 6A
48
Atoms of an Element
ISOTOPES: Stable or Unstable?
Some elements, such as aluminum (Al-27) and arsenic (As-75),
occur naturally as a single type of atom. Many other elements are
mixtures of two or more isotopes. For elements beyond Z = 83, no
stable (i.e. non-radioactive) isotopes exist.
Masses of atoms and percent natural abundances of isotopes are
determined experimentally, relative to a standard.
CHEM 6A
49
How Do We Determine the Isotopic
Makeup of an Element?
Relative Abundance
100 –
50 –
0Relative Mass
Mass Spectrometry: The detector records the positions (mass)
and relative abundances of all particles (or molecular fragments).
CHEM 6A
50
Atomic Masses
AMU: Unit of Measurement
The masses of atoms (and their constituent subatomic particles)
are so small when measured in grams (metric scale) or kg (SI).
For convenience, a relative atomic mass scale is used.
The scale is based on an atom of carbon that contains 6 protons
and 6 neutrons: by convention, it is assigned a mass of exactly 12
atomic mass units (amu, u).
12 amu (u) = Mass of a C-12 atom
” Mass of a C -12 atom % “1.9926465 ×10 -23 g %
-24
1 amu (u) = $
‘=$
‘ = 1.66054 ×10 g
#
& #
12
12
&
CHEM 6A
51
Relative Atomic Masses
All other atomic masses are reported relative to the C-12 standard.
Example: The mass of a single oxygen atom is measured as
2.656764688 x 10-23 g. What is its relative mass (in amu)?
#
&
1 amu
2.656766488 ×10 g × %
= 15.9994 amu
-24 (
$1.66054 ×10 g ‘
-23
Initial quantity
Conversion factor
Equivalent quantity
€
So, if carbon-12 has a mass of 12 amu, why is the listed (standard)
atomic mass of carbon 12.011?
CHEM 6A
52
Isotopes and Atomic Masses
When the isotopic composition of an element is measured, we
obtain the relative masses and natural abundances of atoms very
precisely.
Although mass numbers (A values) are whole numbers, the actual
masses of individual atoms (in amu) are never exact whole
numbers, except for the standard C-12.
Example:
C-12
C-13
C-14
12.000 000 0(0) amu
13.003 354 8378(10) amu
14.003 241 989(4) amu
98.93(8)%
1.07(8)%
0%
For data: http://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl
CHEM 6A
53
Standard Atomic Mass (Weight)
It follows that the standard atomic mass (*weight) of an element
is a weighted average of all its naturally occurring isotopes.
Atomic mass = ∑(Mass of Isotope × Fractional Abundance of Isotope)
Sum
Percent natural abundance / 100
Thus, the average relative atomic mass of carbon =
(12 amu × 0.9893) + (13.00335 amu × 0.0107) = 12.011 amu
Check: Since C-12 atoms are much more abundant than C-13 atoms,
the weighted average must lie closer to 12 than to 13. But remember: No
single carbon atom has a mass of 12.011.
CHEM 6A
54
Polling Q: Standard Atomic Mass
Using the data shown on the mass spectrum below, what is
the relative atomic mass of magnesium?
(A) 24.0 amu
(B) 24.3 amu
(C) 25.0 amu
(D) 26.0 amu
CHEM 6A
55
Class Problem
Lithium* has only two naturally occurring isotopes. The mass of
lithium-6 is 6.01512 amu and the mass of lithium-7 is 7.01601
amu. What is the relative abundance of the two isotopes?
*In the early 1970s, Nobel Laureates Whittingham developed the first functional
lithium-ion battery, and in the following decade, Goodenough found a way to
double the battery’s potential. Yoshino made the battery safer by eliminating the
need for pure lithium, a highly reactive metal.
CHEM 6A
56
Isotopes: Are You Wondering …
Why was Carbon-12 selected as the atomic mass standard? The
International Union of Pure and Applied Chemistry (IUPAC) set this standard in
1961, eliminating earlier discrepancies (mostly arising from significant figures!)
that had resulted from the use of oxygen as mass of 16 amu. Oxygen was
originally used as the standard because it forms so many compounds. In
principle, ANY element could be used as a standard for atomic masses.
If you compared samples of diamond, CO2, and CaCO3, would
the proportions of 12C and 13C be different? The percent abundances
of stable isotopes may vary in samples of the element found in nature.
Since their mass are different, do different isotopes of an
element have different chemical reactivity? No, because the
chemical properties of an element are primarily determined by the number of
electrons.
CHEM 6A
57
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
58
How are the Elements Arranged in the
Periodic Table?
*Weighted average
CHEM 6A
59
Early Tables of the Elements
In the 1800s, scientists started looking for ways to classify the
elements.
Early Tables (Mendeleev, 1871) had elements arranged according
to similar properties, but (incorrectly) as a function of atomic mass.
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60
The Modern Periodic Table
Categories of Elements
In the modern periodic table, elements are listed in order of
increasing atomic number, Z, starting at the upper left.
This arrangement places elements with related chemical and
physical properties in groups (columns), of which there are 18.
The elements in periods (rows), of which there are 7, possess
progressively different chemical and physical properties.
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61
The Modern Periodic Table
Categories of Elements
Period
1
2
3
4
5
6
7
2 elements
8 elements
8 elements
18 elements
18 elements
32 elements
32 elements
All seven periods do not contain the same number of elements.
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62
The Modern Periodic Table
Main group
Categories of Elements
Main group
The “main group” elements consist of eight groups, labeled 1-2
and 13-18 (or 1A-8A).
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63
The Modern Periodic Table
Noble Gases
Halogens
Chalcogens
Main group
Pnictogens
Alkaline Earth Metals
Alkali Metals
Main group
Categories of Elements
The “main group” elements consist of eight groups, labeled 1-2
and 13-18. Six of these groups have characteristic names.
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64
The Modern Periodic Table
Categories of Elements
Transition Metals
In addition to the “main group” elements, there are 10 groups of
transition metals.
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65
The Modern Periodic Table
Categories of Elements
Lanthanides
Actinides
There are also 14 groups of inner transition metals (called the
lanthanides and actinides) placed at bottom to conserve space.
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66
The Modern Periodic Table
Categories of Elements
There are also 14 groups of inner transition metals (called the
lanthanides and actinides) placed at bottom to conserve space.
CHEM 6A
67
The Modern Periodic Table
Alternative Versions (Just for Fun!)
Mohd Abubakr from
Microsoft Research in
Hyderabad, India,
CHEM 6A
68
The Modern Periodic Table
Alternative Versions (Just for Fun!)
CHEM 6A
69
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
70
How are the Elements Classified?
*Weighted average
CHEM 6A
71
The Modern Periodic Table
Classification of Elements
Chemical elements are generally classified:
1. as metals, metalloids, or non-metals;
2. by their physical states (solids, liquids, and gases) at STP;
and
3.
CHEM 6A
by their origin, occurrence, and form on Earth.
72
The Modern Periodic Table
Classification of Elements
CHEM 6A
73
The Modern Periodic Table
1. Classification of Elements – Metallic Character
In the bulk, elements are broadly classified as metals or non-metals:
Non-metal
Metal
•
•
•
Luster (or shine)
Malleable and ductile
Good conductor of
heat and electricity
•
•
•
Dull color
Brittle
Poor conductor of heat
and electricity
Semi-metals or metalloids are elements that have characteristics of both
metals and non-metals.
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74
The Modern Periodic Table
1. Classification of Elements – Metallic Character
Elements on the left-hand side of the periodic table are metallic, while
elements on the right-hand side are non-metallic:
17 elements
are non-metals
Only 7 elements
are metalloids
The semi-metals form a zig-zag line of division.
CHEM 6A
75
The Modern Periodic Table
2. Classification of Elements – Physical States
In the bulk, many lighter elements are gases (e.g. H2, N2, O2, F2, Cl2,
noble gases) and heavier elements are solids (e.g. Bi, P4, Te, I2).
What two elements are found in the liquid state at ambient T/P?
CHEM 6A
76
A Thought Experiment
If you were to embark on an “Element Treasure Hunt” about
campus (or home), how many samples of ‘free or uncombined’
elements could you find?
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77
The Modern Periodic Table
3. Classification of Elements – Origin, Occurrence, Form
•
Following the Big Bang, the universe was comprised mostly of
hydrogen (H) and helium (He).
•
Heavier elements, up to iron (Fe), are formed by fusion of lighter
elements within the core of stars.
•
Supernovae provide the conditions for producing the elements
beyond Fe (Z > 26).
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78
The Modern Periodic Table
3. Classification of Elements – Origin, Occurrence, Form
Of the 118 chemical elements:
•
94 occur naturally on Earth and 24
are synthesized.
•
80 elements have at least one
stable isotope (Z = 83 and below)
and 38 have exclusively radioactive
isotopes (i.e. their nuclei are
unstable and so they undergo
radioactive decay)
•
Stanford Linear Accelerator (1.8 mi)
Fermilab, Illinios (~ 10 mi2)
4 newest (Z = 113, 115, 117, 118)
were named in June, 2016!
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79
The Modern Periodic Table
3. Classification of Elements – Origin, Occurrence, Form
Cosmic and whole-Earth abundances are very different:
Cosmic
Stars are powered by
nuclear
reactions,
primarily the fusion of
hydrogen
to
form
helium. [*15% matter of
universe]
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Crustal
While Fe is the most abundant
element (by mass) on Earth, the
Earth’s crust in made of many
oxides which include SiO2, Al2O3,
FeO, Fe2O3, CaO, MgO, Na2O,
K2O.
Human
Most of the human body is
made of water, H2O;
carbon is the basic unit of
organic molecules.
80
The Modern Periodic Table
3. Classification of Elements – Origin, Occurrence, Form
Given an element’s abundance in a region of the crust, we must next
consider the form in which the element exists on Earth.
Although a few elements occur in an uncombined (native) state, most
are obtained from oxide and sulfide ores (minerals), others from halide
salts, phosphates, carbonates/sulfates, silicates.
CHEM 6A
81
Polling Q: Periodic Facts
Which of the following statements regarding the periodic table is
incorrect?
(A) Reactivity increases down a group.
(B) Hydrogen, in Group 1, is not an alkali metal.
(C) Elements in groups form binary (2 element)
compounds with similar composition.
(D) The largest number of elements are non-metals.
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82
Polling Q: Periodic Trends
Which of the following will have properties that are very different
from the others?
(A) B
(B) Ba
(C) Be
(D) Bi
(E) Br
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83
The Modern Periodic Table
Synopsis
Elements are ordered on the Periodic Table by atomic number, Z.
But why does the Table have the arrangement that it does (i.e. 2
elements in the 1st period but 18 elements in the 4th period?)
The position of an element on the Periodic Table is related to the
electronic structure of its atoms.
Let’s explore next what this means …
CHEM 6A
84
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
85
General Chemistry 6A
(Early) Atomic Models to the Periodic
Table
Fundamentals & Focus 1
Fundamental B and Topic 1A.1
What are the early atomic models? What distinguishes atoms of
different elements? How is the periodic table arranged?
Atomic Theory
CHEM 6A
The Nuclear Atom
The Periodic Table
& Chemical Periodicity
2
Atoms & The Periodic Table
Your Learning Goals
Can you …
•
Apply the Law of Constant Composition and the
Law of Multiple Proportions.
•
Outline Dalton’s Atomic Theory of Matter, and its
shortcomings.
•
Describe the nuclear atom and the experiments that
led to the discovery of subatomic particles.
•
State the number of protons, neutrons, and
electrons in particular atoms and ions (as well as
the mass number, A and the atomic number, Z).
CHEM 6A
I don’t get it!
I need to re-read,
practice problems,
and seek help.
I kind of get it!
I need to re-read
for clarification,
practice problems,
and seek help if I
have questions.
I got it!
I need to engage in
deliberate practice
to reinforce my
understanding.
I got it! I can teach
it to a friend.
I still need to
practice from time to
time (for retention).
3
Atoms & The Periodic Table
Your Learning Goals
Can you …
•
•
•
Calculate the relative atomic mass of an element
(given the percent natural abundances of its stable
(i.e. non-radioactive) isotopes) expressed in
atomic mass units.
Recognize the patterns of chemical reactivity
associated with the chemical elements of the main
group, and thus the general format of the periodic
table.
Classify the chemical elements as metals,
metalloids, or non-metals, by their physical states
(solids, liquids, and gases) at STP, and by their
occurrence, origin, and form on Earth.
CHEM 6A
I don’t get it!
I need to re-read,
practice problems,
and seek help.
I kind of get it!
I need to re-read
for clarification,
practice problems,
and seek help if I
have questions.
I got it!
I need to engage in
deliberate practice
to reinforce my
understanding.
I got it! I can teach
it to a friend.
I still need to
practice from time to
time (for retention).
4
Atomic Theory:
When and How Did We Gain Insight into
the Microscopic World of the Atom?
(“From Caveman to Chemist”, by Hugh W. Salzmann)
CHEM 6A
5
Models of the Atom
As details of its sub-structure were discovered, the model of the
atom has been revised over the last two centuries:
“Billiard ball” “Plum pudding” “Planetary”
model
model
model
1803
1897
1911
“Bohr”
model
1913
“Quantum
mechanical” model
1923 – 1926
Today, the quantum mechanical model provides the most
accurate description of the atom.
CHEM 6A
6
Points to Ponder
What is a scientific model?
produced? tested? refined?
CHEM 6A
What is its purpose? How is it
7
A “Matter” of Time …
5000 B.C.: Troy, etc. … chalks, glass, pigments, textiles, tea
ca. 460-370 B.C.: Democritus’ atomos º indivisible
ca. 50 B.C.: Lucretius “DE RERUM NATURA” (On the Nature of Things)
“All nature consists of twain of things: of atoms and
of the void in which they’re set.”: In other words,
all matter consists of tiny fundamental building
blocks, atoms.
0 B.C.: Greece, Rome – Ancient Alchemy … “air, earth, fire and water”
… medicinal ointments, plant-based medicine
1000: Medieval Europe, Arabic Alchemists … gunpowder, soap and more
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8
A “Matter” of Time …
1700-1800:
Age of Enlightenment … strong acids, alcohols,
microscope, telescope, steam engine, …
Joseph Wright of Derby’s “The
Alchymist, In Search of the
Philosopher’s Stone, Discovers
Phosphorus.” (1771)
CHEM 6A
Chemistry symbols describing alloys,
compounds, chemical operations, etc.
in the 18th century “L’Encylopedia” by
Diderot and D’Alembert
9
The Birth of Modern Chemistry:
Who Took the Intellectual Leap?
1775
1794
1803-8
Antoine Lavoisier
Joseph Proust
John Dalton
The Law of
Conservation of Mass
The Law of
Constant Composition
Atomic Theory of
Matter
http://www.chemheritage.org/explore/explore.html
CHEM 6A
10
Quantitative Analysis à Experimental Data
Late 1700s: Lavoisier and Proust
Law of Constant Composition
Two samples of a given compound are made of the same elements in the
same proportions, no matter their source.
Example: NaCl is always 60.66% chlorine and 39.34% sodium by
mass. So, a 1.00 g sample will contain 0.6066 g Cl and 0.3934 g Na.
Law of Multiple Proportions
Multiple compounds can be made from the same two elements. The
masses of one element which combine with a fixed mass of the second
element are in a ratio of whole numbers.
Example:
compound 1: 16 g of O reacts with 14 g of N
compound 2: 16 g of O reacts with 28 g of N
28/14 = 2 à a small whole number
CHEM 6A
11
Polling Q: Law of Multiple Proportions
Which set of compounds is NOT represented by the data below?
(A) NO and N2O
(B) NO2 and N2O2
(C) NO and NO2
Example:
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compound 1: 16 g of O reacts with 14 g of N
compound 2: 16 g of O reacts with 28 g of N
12
The Atomic Theory
Early 1800s: Dalton
In John Dalton’s “A New System of Chemical Philosophy” (1808),
the evidence for the existence of atoms is marshaled:
1.
2.
3.
4.
All matter consists of extremely small, indivisible particles called atoms.
All atoms of a given element are identical in mass and other properties.
Different chemical elements have different kinds of atoms; in particular, their
atoms have different masses.
A chemical reaction involves a rearrangement of atoms; no atoms are
created, destroyed, or broken apart (Law of Conservation of Mass).
And later …
5.
6.
Compounds are formed when atoms of different elements unite in fixed
proportions (Law of Definite Proportions).
Deduction: More than one compound can be formed from the combination of
two elements; this implies a Law of Multiple Proportions.
CHEM 6A
13
The Atomic Theory
Early 1800s: Dalton
The spheres that Dalton used to demonstrate atomic theory.
Image: Manchester Museum of Science & Industry/SSPL
CHEM 6A
14
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
15
What is the Nuclear (Rutherford)
Model of the Atom?
CHEM 6A
16
The Physical Structure of the Atom:
Is it Really Indivisible?
• Dalton’s Atomic Theory was derived from evidence obtained
at the macroscopic level
However …
• Development of instrumentation capable of probing
phenomena at a microscopic level has given us further
understanding of the atom
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17
The Discovery of Electrons
1897: J.J. Thompson (Cathode Rays)
Cathode rays, or
“current carriers”,
are emitted when a
high potential
difference is applied
between two
electrodes.
Material particles of NEGATIVE charge and unknown mass; The
ratio of the charge to mass (e/me) of the electron are measured.
CHEM 6A
18
Early Atomic Models
1904: Thomson Model of the Atom: A Plum Pudding?
Hypothesis: Neutrality is
provided by a nebulous
cloud of positive charge
CHEM 6A
19
The Discovery of Electrons
1906-14: Robert Millikan (Oil Drop Experiment)
Adjust electric field to
balance two forces:
-Mg = QE
Charge Q is always an
integral multiple of ~
1.6 x 10-19 C.
The charge of the electron, e, (and its mass, me) are determined.
Late 1800s-early 1900s: Many new insights and spin-offs: radiation
CHEM 6A
20
A Detailed Model of the Atom Emerges
1909-1911: Ernest Rutherford (Metal Foil Experiment)
Alpha (a) particle = helium nucleus
(positively charged)
LARGE
deflections
of
alpha-particles
observed: “It was almost as incredible as if
you fired a 15-inch shell at a piece of tissue
paper and it came back and hit you.”
Provides estimation of the atomic radius and identifies positive
charge at center of atom (“nucleus”).
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21
What Makes Up the Nucleus?
1920: Ernest Rutherford
• Hydrogen atom is the fundamental unit of positive charge, +e
• Proposed the term “proton”: different elements have different
numbers of protons in the nucleus of the atom
1932: James Chadwick
• Discovered the “neutron”, which has mass but no charge
• Role in stability: prevents electrostatic repulsions between
protons and the dissociation of the nucleus
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22
Nuclear Model of the Atom
Atoms, which are electrically neutral, are made of three subatomic particles: protons (p), electrons (e-) and neutrons (n).
uncharged
positively charged
(+e)
negatively charged
(-e)
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23
Nuclear Model of the Atom
Electrons have a mass that 1/1836 times that of a proton or a
neutron! We’ll see shortly how we express the absolute mass
(kg or g) in terms of a relative mass (amu).
CHEM 6A
24
Nuclear Model of the Atom
The elementary charge (e) is 1.602 x 10-19 C (Coulombs).
In atomic (or relative) units, the electron is assigned a charge of -1,
and the proton is assigned a charge of +1. The charges are equal
in magnitude but opposite in sign.
CHEM 6A
25
Nuclear Model of the Atom
The nucleus is at the center of the atom and contains the protons
and neutrons. The electrons move rapidly through a large, mostly
empty volume of space about the nucleus.
Charge on nucleus is +Ze,
where Z = number of protons.
It follows that Z electrons
must surround the nucleus.
Since electrons “weigh” so little, virtually all the mass of an atom
is concentrated in the nucleus.
CHEM 6A
26
Nuclear Model of the Atom
Measurements show that the diameter of a nucleus is about 10-15
m, whereas the atom itself is about 10-10 m wide.*
* These values depend on the element.
CHEM 6A
27
Atomic Structure
In Perspective
If an atom was the diameter of our 1200 acre (4.85 x 106 m2) campus,
the nucleus would be about the size of a U.S. quarter (25 mm).
CHEM 6A
28
Atomic Structure
In Perspective
Approximately how many atoms can you line up across the
widest part of a pinhead that measures 1 mm in diameter?
1 atom
10 −10 m
1m
1 mm
7 atoms
× 3
×
= 10
or 10 million atoms!!!
10 mm
pinhead
pinhead
Figure from: http://www.nclt.us/grg/23011.pdf
CHEM 6A
29
Atomic Structure
What is the “Glue” Holding Together the Atom?
The structure of an atom is determined by an interplay of
different forces.
• Electrostatic (Coulombic) forces keep electrons apart
(repulsion of like charges) but draw them to the protons in the
nucleus (attraction of opposite charges).
• Protons in the nucleus are held together by a strong nuclear
force, one of the 4 known forces in the universe.
CHEM 6A
30
Are You Wondering?
A study of matter at its most fundamental level must consider
many additional subatomic particles (beyond neutrons, protons,
and electrons). This is the subject of elementary particle physics,
rather than chemistry.
If you’re wondering about quarks, leptons, and
bosons, watch the video titled CERN, the
European Organization for Nuclear Research:

CHEM 6A
31
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
32
So What Makes Atoms of One Element
Different from Another?
A
E
Z
CHEM 6A
33
Atoms of an Element
Number of Protons (Atomic Number, Z)
ALL atoms of a given element possess the same number of
protons (p) in their nuclei. This value is unique to each element
and is called its atomic number (Z).
Examples:
1p
6p
8p
hydrogen
Z=1
carbon
Z=6
oxygen
Z=8
That is, if an atom has 1 proton, then its atomic number is 1, and it is
hydrogen. If an atom is hydrogen, it has 1 proton.
CHEM 6A
34
Atoms of an Element
Number of Electrons
Since an atom is electrically neutral, it follows that:
number of electrons = number of protons (Z)
Examples:
€
1p
1e-
hydrogen
Z=1
6p
6e-
carbon
Z=6
8p
8e-
oxygen
Z=8
So, if a carbon atom (Z = 6) has 6 protons, it must also have 6 electrons
surrounding its nucleus, and so on.
CHEM 6A
35
Atoms of an Element
Number of Neutrons (N)
The number of neutrons (N) in an atom of a given element may
vary.* Except for hydrogen, N is always equal to or greater than
the number of protons in the nucleus.
Examples:
1p
1e-
6p
6n
6e-
8p
8n
8e-
hydrogen
Z=1
carbon
Z=6
oxygen
Z=8
N=0
N=6
N=8
* There is no simple way to predict how many neutrons a given atom will
have.
CHEM 6A
36
Atoms of an Element
Mass Number, A = N + Z
Electrons have negligible mass, so it is the total number of protons
and neutrons in the nucleus of the atom that define its mass
number (A).
Examples:
CHEM 6A
1p
1e-
6p
6n
6e-
8p
8n
8e-
hydrogen
Z=1
carbon
Z=6
oxygen
Z=8
N=0
A=1
N=6
A = 12
N=8
A = 16
37
Atoms of an Element
Common Notations
In representing the composition of an atom, the atomic number and
mass number are often included with the atomic symbol:
A
Z
E
E = Chemical symbol of an element
A = Mass Number = p + n
Z = Atomic Number = p
A
E
In a different notation, the chemical symbol (or chemical name) is
followed by a dash and the mass number.
E-A
CHEM 6A
Element Name-A
38
Atoms of an Element
Common Notations
We can apply these notations to our previous examples:
Examples:
1p
1
1
H or 1H
hydrogen-1
H-1
€
€
6p
6n
1e
12
6
8p
8n
6e
C or 12C
carbon-12
C-12
16
8
8e
O or 16O
oxygen-16
O-16
€
The mass number, A, is important for distinguishing isotopes.
CHEM 6A
39
Polling Q: Atomic Symbols
An atom of uranium-235 (Z = 92) has how many protons
(p), electrons (e-), and neutrons (n) ?
(A) 92 p, 92 e-, 143 n
(B) 92 p, 43 e-, 235 n
(C) 92 p, 92 e-, 235 n
(D) 235 p, 235 e-, 143 n
CHEM 6A
40
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
41
What is the Difference Between an
Isotope and an Ion?
A
E
Z
CHEM 6A
42
Atoms of an Element
Different Neutron Counts: ISOTOPES
Isotopes are atoms of an element that have different numbers of
neutrons (N), and thus, different mass numbers (A).
Example: A sample of hydrogen atoms consists of …
1
1
1
H (hydrogen)
99.985%
!
These atoms
possess
!
(because of e- counts).
1
2
1
H (deuterium)
0.015%
nearly
identical
!
1
3
1
H (tritium)
0% (synthesized in nuclear reactor)
chemical
properties
Dalton’s postulate was incorrect: Atoms of a given element may not be identical in mass!
CHEM 6A
43
Atoms of an Element
Different Electron Counts: IONS
A (monatomic) ion is a charged particle formed when a neutral
atom loses or gains one or more electrons.
CATION: a positively charged ion.
ANION: a negatively charged ion.
The symbol for an ion is written by adding the electrical charge as
a superscript to the right of the symbol for the element.
Example: Na ® Na+ + e11p 10e12n
CHEM 6A
Example: Cl + e- ® Cl−
17p 18e18n
44
Class Problem
24
25
24
16
CHEM 6A
Mg
Mg
Mg2+
O2-
# of protons
# of electrons
# of neutrons
12
12
12
?
12
13
?
?
?
?
?
?
A
E
Z
45
Polling Q: Electrons and Protons
In which of the following sets do all species have the same
number of electrons (i.e., are isoelectronic)?
(A) K+, Rb+, Cs+
(B) Cl-, Ar, Ca2+
(C) Br, Br-, Br+
(D) C, N3-, O2-
CHEM 6A
46
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
47
How Do We Calculate Atomic Mass?
CHEM 6A
48
Atoms of an Element
ISOTOPES: Stable or Unstable?
Some elements, such as aluminum (Al-27) and arsenic (As-75),
occur naturally as a single type of atom. Many other elements are
mixtures of two or more isotopes. For elements beyond Z = 83, no
stable (i.e. non-radioactive) isotopes exist.
Masses of atoms and percent natural abundances of isotopes are
determined experimentally, relative to a standard.
CHEM 6A
49
How Do We Determine the Isotopic
Makeup of an Element?
Relative Abundance
100 –
50 –
0Relative Mass
Mass Spectrometry: The detector records the positions (mass)
and relative abundances of all particles (or molecular fragments).
CHEM 6A
50
Atomic Masses
AMU: Unit of Measurement
The masses of atoms (and their constituent subatomic particles)
are so small when measured in grams (metric scale) or kg (SI).
For convenience, a relative atomic mass scale is used.
The scale is based on an atom of carbon that contains 6 protons
and 6 neutrons: by convention, it is assigned a mass of exactly 12
atomic mass units (amu, u).
12 amu (u) = Mass of a C-12 atom
” Mass of a C -12 atom % “1.9926465 ×10 -23 g %
-24
1 amu (u) = $
‘=$
‘ = 1.66054 ×10 g
#
& #
12
12
&
CHEM 6A
51
Relative Atomic Masses
All other atomic masses are reported relative to the C-12 standard.
Example: The mass of a single oxygen atom is measured as
2.656764688 x 10-23 g. What is its relative mass (in amu)?
#
&
1 amu
2.656766488 ×10 g × %
= 15.9994 amu
-24 (
$1.66054 ×10 g ‘
-23
Initial quantity
Conversion factor
Equivalent quantity
€
So, if carbon-12 has a mass of 12 amu, why is the listed (standard)
atomic mass of carbon 12.011?
CHEM 6A
52
Isotopes and Atomic Masses
When the isotopic composition of an element is measured, we
obtain the relative masses and natural abundances of atoms very
precisely.
Although mass numbers (A values) are whole numbers, the actual
masses of individual atoms (in amu) are never exact whole
numbers, except for the standard C-12.
Example:
C-12
C-13
C-14
12.000 000 0(0) amu
13.003 354 8378(10) amu
14.003 241 989(4) amu
98.93(8)%
1.07(8)%
0%
For data: http://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl
CHEM 6A
53
Standard Atomic Mass (Weight)
It follows that the standard atomic mass (*weight) of an element
is a weighted average of all its naturally occurring isotopes.
Atomic mass = ∑(Mass of Isotope × Fractional Abundance of Isotope)
Sum
Percent natural abundance / 100
Thus, the average relative atomic mass of carbon =
(12 amu × 0.9893) + (13.00335 amu × 0.0107) = 12.011 amu
Check: Since C-12 atoms are much more abundant than C-13 atoms,
the weighted average must lie closer to 12 than to 13. But remember: No
single carbon atom has a mass of 12.011.
CHEM 6A
54
Polling Q: Standard Atomic Mass
Using the data shown on the mass spectrum below, what is
the relative atomic mass of magnesium?
(A) 24.0 amu
(B) 24.3 amu
(C) 25.0 amu
(D) 26.0 amu
CHEM 6A
55
Class Problem
Lithium* has only two naturally occurring isotopes. The mass of
lithium-6 is 6.01512 amu and the mass of lithium-7 is 7.01601
amu. What is the relative abundance of the two isotopes?
*In the early 1970s, Nobel Laureates Whittingham developed the first functional
lithium-ion battery, and in the following decade, Goodenough found a way to
double the battery’s potential. Yoshino made the battery safer by eliminating the
need for pure lithium, a highly reactive metal.
CHEM 6A
56
Isotopes: Are You Wondering …
Why was Carbon-12 selected as the atomic mass standard? The
International Union of Pure and Applied Chemistry (IUPAC) set this standard in
1961, eliminating earlier discrepancies (mostly arising from significant figures!)
that had resulted from the use of oxygen as mass of 16 amu. Oxygen was
originally used as the standard because it forms so many compounds. In
principle, ANY element could be used as a standard for atomic masses.
If you compared samples of diamond, CO2, and CaCO3, would
the proportions of 12C and 13C be different? The percent abundances
of stable isotopes may vary in samples of the element found in nature.
Since their mass are different, do different isotopes of an
element have different chemical reactivity? No, because the
chemical properties of an element are primarily determined by the number of
electrons.
CHEM 6A
57
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
58
How are the Elements Arranged in the
Periodic Table?
*Weighted average
CHEM 6A
59
Early Tables of the Elements
In the 1800s, scientists started looking for ways to classify the
elements.
Early Tables (Mendeleev, 1871) had elements arranged according
to similar properties, but (incorrectly) as a function of atomic mass.
CHEM 6A
60
The Modern Periodic Table
Categories of Elements
In the modern periodic table, elements are listed in order of
increasing atomic number, Z, starting at the upper left.
This arrangement places elements with related chemical and
physical properties in groups (columns), of which there are 18.
The elements in periods (rows), of which there are 7, possess
progressively different chemical and physical properties.
CHEM 6A
61
The Modern Periodic Table
Categories of Elements
Period
1
2
3
4
5
6
7
2 elements
8 elements
8 elements
18 elements
18 elements
32 elements
32 elements
All seven periods do not contain the same number of elements.
CHEM 6A
62
The Modern Periodic Table
Main group
Categories of Elements
Main group
The “main group” elements consist of eight groups, labeled 1-2
and 13-18 (or 1A-8A).
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63
The Modern Periodic Table
Noble Gases
Halogens
Chalcogens
Main group
Pnictogens
Alkaline Earth Metals
Alkali Metals
Main group
Categories of Elements
The “main group” elements consist of eight groups, labeled 1-2
and 13-18. Six of these groups have characteristic names.
CHEM 6A
64
The Modern Periodic Table
Categories of Elements
Transition Metals
In addition to the “main group” elements, there are 10 groups of
transition metals.
CHEM 6A
65
The Modern Periodic Table
Categories of Elements
Lanthanides
Actinides
There are also 14 groups of inner transition metals (called the
lanthanides and actinides) placed at bottom to conserve space.
CHEM 6A
66
The Modern Periodic Table
Categories of Elements
There are also 14 groups of inner transition metals (called the
lanthanides and actinides) placed at bottom to conserve space.
CHEM 6A
67
The Modern Periodic Table
Alternative Versions (Just for Fun!)
Mohd Abubakr from
Microsoft Research in
Hyderabad, India,
CHEM 6A
68
The Modern Periodic Table
Alternative Versions (Just for Fun!)
CHEM 6A
69
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
70
How are the Elements Classified?
*Weighted average
CHEM 6A
71
The Modern Periodic Table
Classification of Elements
Chemical elements are generally classified:
1. as metals, metalloids, or non-metals;
2. by their physical states (solids, liquids, and gases) at STP;
and
3.
CHEM 6A
by their origin, occurrence, and form on Earth.
72
The Modern Periodic Table
Classification of Elements
CHEM 6A
73
The Modern Periodic Table
1. Classification of Elements – Metallic Character
In the bulk, elements are broadly classified as metals or non-metals:
Non-metal
Metal
•
•
•
Luster (or shine)
Malleable and ductile
Good conductor of
heat and electricity
•
•
•
Dull color
Brittle
Poor conductor of heat
and electricity
Semi-metals or metalloids are elements that have characteristics of both
metals and non-metals.
CHEM 6A
74
The Modern Periodic Table
1. Classification of Elements – Metallic Character
Elements on the left-hand side of the periodic table are metallic, while
elements on the right-hand side are non-metallic:
17 elements
are non-metals
Only 7 elements
are metalloids
The semi-metals form a zig-zag line of division.
CHEM 6A
75
The Modern Periodic Table
2. Classification of Elements – Physical States
In the bulk, many lighter elements are gases (e.g. H2, N2, O2, F2, Cl2,
noble gases) and heavier elements are solids (e.g. Bi, P4, Te, I2).
What two elements are found in the liquid state at ambient T/P?
CHEM 6A
76
A Thought Experiment
If you were to embark on an “Element Treasure Hunt” about
campus (or home), how many samples of ‘free or uncombined’
elements could you find?
CHEM 6A
77
The Modern Periodic Table
3. Classification of Elements – Origin, Occurrence, Form
•
Following the Big Bang, the universe was comprised mostly of
hydrogen (H) and helium (He).
•
Heavier elements, up to iron (Fe), are formed by fusion of lighter
elements within the core of stars.
•
Supernovae provide the conditions for producing the elements
beyond Fe (Z > 26).
CHEM 6A
78
The Modern Periodic Table
3. Classification of Elements – Origin, Occurrence, Form
Of the 118 chemical elements:
•
94 occur naturally on Earth and 24
are synthesized.
•
80 elements have at least one
stable isotope (Z = 83 and below)
and 38 have exclusively radioactive
isotopes (i.e. their nuclei are
unstable and so they undergo
radioactive decay)
•
Stanford Linear Accelerator (1.8 mi)
Fermilab, Illinios (~ 10 mi2)
4 newest (Z = 113, 115, 117, 118)
were named in June, 2016!
CHEM 6A
79
The Modern Periodic Table
3. Classification of Elements – Origin, Occurrence, Form
Cosmic and whole-Earth abundances are very different:
Cosmic
Stars are powered by
nuclear
reactions,
primarily the fusion of
hydrogen
to
form
helium. [*15% matter of
universe]
CHEM 6A
Crustal
While Fe is the most abundant
element (by mass) on Earth, the
Earth’s crust in made of many
oxides which include SiO2, Al2O3,
FeO, Fe2O3, CaO, MgO, Na2O,
K2O.
Human
Most of the human body is
made of water, H2O;
carbon is the basic unit of
organic molecules.
80
The Modern Periodic Table
3. Classification of Elements – Origin, Occurrence, Form
Given an element’s abundance in a region of the crust, we must next
consider the form in which the element exists on Earth.
Although a few elements occur in an uncombined (native) state, most
are obtained from oxide and sulfide ores (minerals), others from halide
salts, phosphates, carbonates/sulfates, silicates.
CHEM 6A
81
Polling Q: Periodic Facts
Which of the following statements regarding the periodic table is
incorrect?
(A) Reactivity increases down a group.
(B) Hydrogen, in Group 1, is not an alkali metal.
(C) Elements in groups form binary (2 element)
compounds with similar composition.
(D) The largest number of elements are non-metals.
CHEM 6A
82
Polling Q: Periodic Trends
Which of the following will have properties that are very different
from the others?
(A) B
(B) Ba
(C) Be
(D) Bi
(E) Br
CHEM 6A
83
The Modern Periodic Table
Synopsis
Elements are ordered on the Periodic Table by atomic number, Z.
But why does the Table have the arrangement that it does (i.e. 2
elements in the 1st period but 18 elements in the 4th period?)
The position of an element on the Periodic Table is related to the
electronic structure of its atoms.
Let’s explore next what this means …
CHEM 6A
84
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
85
General Chemistry 6A
(Early) Atomic Models to the Periodic
Table
Fundamentals & Focus 1
Fundamental B and Topic 1A.1
What are the early atomic models? What distinguishes atoms of
different elements? How is the periodic table arranged?
Atomic Theory
CHEM 6A
The Nuclear Atom
The Periodic Table
& Chemical Periodicity
2
Atoms & The Periodic Table
Your Learning Goals
Can you …
•
Apply the Law of Constant Composition and the
Law of Multiple Proportions.
•
Outline Dalton’s Atomic Theory of Matter, and its
shortcomings.
•
Describe the nuclear atom and the experiments that
led to the discovery of subatomic particles.
•
State the number of protons, neutrons, and
electrons in particular atoms and ions (as well as
the mass number, A and the atomic number, Z).
CHEM 6A
I don’t get it!
I need to re-read,
practice problems,
and seek help.
I kind of get it!
I need to re-read
for clarification,
practice problems,
and seek help if I
have questions.
I got it!
I need to engage in
deliberate practice
to reinforce my
understanding.
I got it! I can teach
it to a friend.
I still need to
practice from time to
time (for retention).
3
Atoms & The Periodic Table
Your Learning Goals
Can you …
•
•
•
Calculate the relative atomic mass of an element
(given the percent natural abundances of its stable
(i.e. non-radioactive) isotopes) expressed in
atomic mass units.
Recognize the patterns of chemical reactivity
associated with the chemical elements of the main
group, and thus the general format of the periodic
table.
Classify the chemical elements as metals,
metalloids, or non-metals, by their physical states
(solids, liquids, and gases) at STP, and by their
occurrence, origin, and form on Earth.
CHEM 6A
I don’t get it!
I need to re-read,
practice problems,
and seek help.
I kind of get it!
I need to re-read
for clarification,
practice problems,
and seek help if I
have questions.
I got it!
I need to engage in
deliberate practice
to reinforce my
understanding.
I got it! I can teach
it to a friend.
I still need to
practice from time to
time (for retention).
4
Atomic Theory:
When and How Did We Gain Insight into
the Microscopic World of the Atom?
(“From Caveman to Chemist”, by Hugh W. Salzmann)
CHEM 6A
5
Models of the Atom
As details of its sub-structure were discovered, the model of the
atom has been revised over the last two centuries:
“Billiard ball” “Plum pudding” “Planetary”
model
model
model
1803
1897
1911
“Bohr”
model
1913
“Quantum
mechanical” model
1923 – 1926
Today, the quantum mechanical model provides the most
accurate description of the atom.
CHEM 6A
6
Points to Ponder
What is a scientific model?
produced? tested? refined?
CHEM 6A
What is its purpose? How is it
7
A “Matter” of Time …
5000 B.C.: Troy, etc. … chalks, glass, pigments, textiles, tea
ca. 460-370 B.C.: Democritus’ atomos º indivisible
ca. 50 B.C.: Lucretius “DE RERUM NATURA” (On the Nature of Things)
“All nature consists of twain of things: of atoms and
of the void in which they’re set.”: In other words,
all matter consists of tiny fundamental building
blocks, atoms.
0 B.C.: Greece, Rome – Ancient Alchemy … “air, earth, fire and water”
… medicinal ointments, plant-based medicine
1000: Medieval Europe, Arabic Alchemists … gunpowder, soap and more
CHEM 6A
8
A “Matter” of Time …
1700-1800:
Age of Enlightenment … strong acids, alcohols,
microscope, telescope, steam engine, …
Joseph Wright of Derby’s “The
Alchymist, In Search of the
Philosopher’s Stone, Discovers
Phosphorus.” (1771)
CHEM 6A
Chemistry symbols describing alloys,
compounds, chemical operations, etc.
in the 18th century “L’Encylopedia” by
Diderot and D’Alembert
9
The Birth of Modern Chemistry:
Who Took the Intellectual Leap?
1775
1794
1803-8
Antoine Lavoisier
Joseph Proust
John Dalton
The Law of
Conservation of Mass
The Law of
Constant Composition
Atomic Theory of
Matter
http://www.chemheritage.org/explore/explore.html
CHEM 6A
10
Quantitative Analysis à Experimental Data
Late 1700s: Lavoisier and Proust
Law of Constant Composition
Two samples of a given compound are made of the same elements in the
same proportions, no matter their source.
Example: NaCl is always 60.66% chlorine and 39.34% sodium by
mass. So, a 1.00 g sample will contain 0.6066 g Cl and 0.3934 g Na.
Law of Multiple Proportions
Multiple compounds can be made from the same two elements. The
masses of one element which combine with a fixed mass of the second
element are in a ratio of whole numbers.
Example:
compound 1: 16 g of O reacts with 14 g of N
compound 2: 16 g of O reacts with 28 g of N
28/14 = 2 à a small whole number
CHEM 6A
11
Polling Q: Law of Multiple Proportions
Which set of compounds is NOT represented by the data below?
(A) NO and N2O
(B) NO2 and N2O2
(C) NO and NO2
Example:
CHEM 6A
compound 1: 16 g of O reacts with 14 g of N
compound 2: 16 g of O reacts with 28 g of N
12
The Atomic Theory
Early 1800s: Dalton
In John Dalton’s “A New System of Chemical Philosophy” (1808),
the evidence for the existence of atoms is marshaled:
1.
2.
3.
4.
All matter consists of extremely small, indivisible particles called atoms.
All atoms of a given element are identical in mass and other properties.
Different chemical elements have different kinds of atoms; in particular, their
atoms have different masses.
A chemical reaction involves a rearrangement of atoms; no atoms are
created, destroyed, or broken apart (Law of Conservation of Mass).
And later …
5.
6.
Compounds are formed when atoms of different elements unite in fixed
proportions (Law of Definite Proportions).
Deduction: More than one compound can be formed from the combination of
two elements; this implies a Law of Multiple Proportions.
CHEM 6A
13
The Atomic Theory
Early 1800s: Dalton
The spheres that Dalton used to demonstrate atomic theory.
Image: Manchester Museum of Science & Industry/SSPL
CHEM 6A
14
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
15
What is the Nuclear (Rutherford)
Model of the Atom?
CHEM 6A
16
The Physical Structure of the Atom:
Is it Really Indivisible?
• Dalton’s Atomic Theory was derived from evidence obtained
at the macroscopic level
However …
• Development of instrumentation capable of probing
phenomena at a microscopic level has given us further
understanding of the atom
CHEM 6A
17
The Discovery of Electrons
1897: J.J. Thompson (Cathode Rays)
Cathode rays, or
“current carriers”,
are emitted when a
high potential
difference is applied
between two
electrodes.
Material particles of NEGATIVE charge and unknown mass; The
ratio of the charge to mass (e/me) of the electron are measured.
CHEM 6A
18
Early Atomic Models
1904: Thomson Model of the Atom: A Plum Pudding?
Hypothesis: Neutrality is
provided by a nebulous
cloud of positive charge
CHEM 6A
19
The Discovery of Electrons
1906-14: Robert Millikan (Oil Drop Experiment)
Adjust electric field to
balance two forces:
-Mg = QE
Charge Q is always an
integral multiple of ~
1.6 x 10-19 C.
The charge of the electron, e, (and its mass, me) are determined.
Late 1800s-early 1900s: Many new insights and spin-offs: radiation
CHEM 6A
20
A Detailed Model of the Atom Emerges
1909-1911: Ernest Rutherford (Metal Foil Experiment)
Alpha (a) particle = helium nucleus
(positively charged)
LARGE
deflections
of
alpha-particles
observed: “It was almost as incredible as if
you fired a 15-inch shell at a piece of tissue
paper and it came back and hit you.”
Provides estimation of the atomic radius and identifies positive
charge at center of atom (“nucleus”).
CHEM 6A
21
What Makes Up the Nucleus?
1920: Ernest Rutherford
• Hydrogen atom is the fundamental unit of positive charge, +e
• Proposed the term “proton”: different elements have different
numbers of protons in the nucleus of the atom
1932: James Chadwick
• Discovered the “neutron”, which has mass but no charge
• Role in stability: prevents electrostatic repulsions between
protons and the dissociation of the nucleus
CHEM 6A
22
Nuclear Model of the Atom
Atoms, which are electrically neutral, are made of three subatomic particles: protons (p), electrons (e-) and neutrons (n).
uncharged
positively charged
(+e)
negatively charged
(-e)
CHEM 6A
23
Nuclear Model of the Atom
Electrons have a mass that 1/1836 times that of a proton or a
neutron! We’ll see shortly how we express the absolute mass
(kg or g) in terms of a relative mass (amu).
CHEM 6A
24
Nuclear Model of the Atom
The elementary charge (e) is 1.602 x 10-19 C (Coulombs).
In atomic (or relative) units, the electron is assigned a charge of -1,
and the proton is assigned a charge of +1. The charges are equal
in magnitude but opposite in sign.
CHEM 6A
25
Nuclear Model of the Atom
The nucleus is at the center of the atom and contains the protons
and neutrons. The electrons move rapidly through a large, mostly
empty volume of space about the nucleus.
Charge on nucleus is +Ze,
where Z = number of protons.
It follows that Z electrons
must surround the nucleus.
Since electrons “weigh” so little, virtually all the mass of an atom
is concentrated in the nucleus.
CHEM 6A
26
Nuclear Model of the Atom
Measurements show that the diameter of a nucleus is about 10-15
m, whereas the atom itself is about 10-10 m wide.*
* These values depend on the element.
CHEM 6A
27
Atomic Structure
In Perspective
If an atom was the diameter of our 1200 acre (4.85 x 106 m2) campus,
the nucleus would be about the size of a U.S. quarter (25 mm).
CHEM 6A
28
Atomic Structure
In Perspective
Approximately how many atoms can you line up across the
widest part of a pinhead that measures 1 mm in diameter?
1 atom
10 −10 m
1m
1 mm
7 atoms
× 3
×
= 10
or 10 million atoms!!!
10 mm
pinhead
pinhead
Figure from: http://www.nclt.us/grg/23011.pdf
CHEM 6A
29
Atomic Structure
What is the “Glue” Holding Together the Atom?
The structure of an atom is determined by an interplay of
different forces.
• Electrostatic (Coulombic) forces keep electrons apart
(repulsion of like charges) but draw them to the protons in the
nucleus (attraction of opposite charges).
• Protons in the nucleus are held together by a strong nuclear
force, one of the 4 known forces in the universe.
CHEM 6A
30
Are You Wondering?
A study of matter at its most fundamental level must consider
many additional subatomic particles (beyond neutrons, protons,
and electrons). This is the subject of elementary particle physics,
rather than chemistry.
If you’re wondering about quarks, leptons, and
bosons, watch the video titled CERN, the
European Organization for Nuclear Research:

CHEM 6A
31
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
32
So What Makes Atoms of One Element
Different from Another?
A
E
Z
CHEM 6A
33
Atoms of an Element
Number of Protons (Atomic Number, Z)
ALL atoms of a given element possess the same number of
protons (p) in their nuclei. This value is unique to each element
and is called its atomic number (Z).
Examples:
1p
6p
8p
hydrogen
Z=1
carbon
Z=6
oxygen
Z=8
That is, if an atom has 1 proton, then its atomic number is 1, and it is
hydrogen. If an atom is hydrogen, it has 1 proton.
CHEM 6A
34
Atoms of an Element
Number of Electrons
Since an atom is electrically neutral, it follows that:
number of electrons = number of protons (Z)
Examples:
€
1p
1e-
hydrogen
Z=1
6p
6e-
carbon
Z=6
8p
8e-
oxygen
Z=8
So, if a carbon atom (Z = 6) has 6 protons, it must also have 6 electrons
surrounding its nucleus, and so on.
CHEM 6A
35
Atoms of an Element
Number of Neutrons (N)
The number of neutrons (N) in an atom of a given element may
vary.* Except for hydrogen, N is always equal to or greater than
the number of protons in the nucleus.
Examples:
1p
1e-
6p
6n
6e-
8p
8n
8e-
hydrogen
Z=1
carbon
Z=6
oxygen
Z=8
N=0
N=6
N=8
* There is no simple way to predict how many neutrons a given atom will
have.
CHEM 6A
36
Atoms of an Element
Mass Number, A = N + Z
Electrons have negligible mass, so it is the total number of protons
and neutrons in the nucleus of the atom that define its mass
number (A).
Examples:
CHEM 6A
1p
1e-
6p
6n
6e-
8p
8n
8e-
hydrogen
Z=1
carbon
Z=6
oxygen
Z=8
N=0
A=1
N=6
A = 12
N=8
A = 16
37
Atoms of an Element
Common Notations
In representing the composition of an atom, the atomic number and
mass number are often included with the atomic symbol:
A
Z
E
E = Chemical symbol of an element
A = Mass Number = p + n
Z = Atomic Number = p
A
E
In a different notation, the chemical symbol (or chemical name) is
followed by a dash and the mass number.
E-A
CHEM 6A
Element Name-A
38
Atoms of an Element
Common Notations
We can apply these notations to our previous examples:
Examples:
1p
1
1
H or 1H
hydrogen-1
H-1
€
€
6p
6n
1e
12
6
8p
8n
6e
C or 12C
carbon-12
C-12
16
8
8e
O or 16O
oxygen-16
O-16
€
The mass number, A, is important for distinguishing isotopes.
CHEM 6A
39
Polling Q: Atomic Symbols
An atom of uranium-235 (Z = 92) has how many protons
(p), electrons (e-), and neutrons (n) ?
(A) 92 p, 92 e-, 143 n
(B) 92 p, 43 e-, 235 n
(C) 92 p, 92 e-, 235 n
(D) 235 p, 235 e-, 143 n
CHEM 6A
40
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
41
What is the Difference Between an
Isotope and an Ion?
A
E
Z
CHEM 6A
42
Atoms of an Element
Different Neutron Counts: ISOTOPES
Isotopes are atoms of an element that have different numbers of
neutrons (N), and thus, different mass numbers (A).
Example: A sample of hydrogen atoms consists of …
1
1
1
H (hydrogen)
99.985%
!
These atoms
possess
!
(because of e- counts).
1
2
1
H (deuterium)
0.015%
nearly
identical
!
1
3
1
H (tritium)
0% (synthesized in nuclear reactor)
chemical
properties
Dalton’s postulate was incorrect: Atoms of a given element may not be identical in mass!
CHEM 6A
43
Atoms of an Element
Different Electron Counts: IONS
A (monatomic) ion is a charged particle formed when a neutral
atom loses or gains one or more electrons.
CATION: a positively charged ion.
ANION: a negatively charged ion.
The symbol for an ion is written by adding the electrical charge as
a superscript to the right of the symbol for the element.
Example: Na ® Na+ + e11p 10e12n
CHEM 6A
Example: Cl + e- ® Cl−
17p 18e18n
44
Class Problem
24
25
24
16
CHEM 6A
Mg
Mg
Mg2+
O2-
# of protons
# of electrons
# of neutrons
12
12
12
?
12
13
?
?
?
?
?
?
A
E
Z
45
Polling Q: Electrons and Protons
In which of the following sets do all species have the same
number of electrons (i.e., are isoelectronic)?
(A) K+, Rb+, Cs+
(B) Cl-, Ar, Ca2+
(C) Br, Br-, Br+
(D) C, N3-, O2-
CHEM 6A
46
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
47
How Do We Calculate Atomic Mass?
CHEM 6A
48
Atoms of an Element
ISOTOPES: Stable or Unstable?
Some elements, such as aluminum (Al-27) and arsenic (As-75),
occur naturally as a single type of atom. Many other elements are
mixtures of two or more isotopes. For elements beyond Z = 83, no
stable (i.e. non-radioactive) isotopes exist.
Masses of atoms and percent natural abundances of isotopes are
determined experimentally, relative to a standard.
CHEM 6A
49
How Do We Determine the Isotopic
Makeup of an Element?
Relative Abundance
100 –
50 –
0Relative Mass
Mass Spectrometry: The detector records the positions (mass)
and relative abundances of all particles (or molecular fragments).
CHEM 6A
50
Atomic Masses
AMU: Unit of Measurement
The masses of atoms (and their constituent subatomic particles)
are so small when measured in grams (metric scale) or kg (SI).
For convenience, a relative atomic mass scale is used.
The scale is based on an atom of carbon that contains 6 protons
and 6 neutrons: by convention, it is assigned a mass of exactly 12
atomic mass units (amu, u).
12 amu (u) = Mass of a C-12 atom
” Mass of a C -12 atom % “1.9926465 ×10 -23 g %
-24
1 amu (u) = $
‘=$
‘ = 1.66054 ×10 g
#
& #
12
12
&
CHEM 6A
51
Relative Atomic Masses
All other atomic masses are reported relative to the C-12 standard.
Example: The mass of a single oxygen atom is measured as
2.656764688 x 10-23 g. What is its relative mass (in amu)?
#
&
1 amu
2.656766488 ×10 g × %
= 15.9994 amu
-24 (
$1.66054 ×10 g ‘
-23
Initial quantity
Conversion factor
Equivalent quantity
€
So, if carbon-12 has a mass of 12 amu, why is the listed (standard)
atomic mass of carbon 12.011?
CHEM 6A
52
Isotopes and Atomic Masses
When the isotopic composition of an element is measured, we
obtain the relative masses and natural abundances of atoms very
precisely.
Although mass numbers (A values) are whole numbers, the actual
masses of individual atoms (in amu) are never exact whole
numbers, except for the standard C-12.
Example:
C-12
C-13
C-14
12.000 000 0(0) amu
13.003 354 8378(10) amu
14.003 241 989(4) amu
98.93(8)%
1.07(8)%
0%
For data: http://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl
CHEM 6A
53
Standard Atomic Mass (Weight)
It follows that the standard atomic mass (*weight) of an element
is a weighted average of all its naturally occurring isotopes.
Atomic mass = ∑(Mass of Isotope × Fractional Abundance of Isotope)
Sum
Percent natural abundance / 100
Thus, the average relative atomic mass of carbon =
(12 amu × 0.9893) + (13.00335 amu × 0.0107) = 12.011 amu
Check: Since C-12 atoms are much more abundant than C-13 atoms,
the weighted average must lie closer to 12 than to 13. But remember: No
single carbon atom has a mass of 12.011.
CHEM 6A
54
Polling Q: Standard Atomic Mass
Using the data shown on the mass spectrum below, what is
the relative atomic mass of magnesium?
(A) 24.0 amu
(B) 24.3 amu
(C) 25.0 amu
(D) 26.0 amu
CHEM 6A
55
Class Problem
Lithium* has only two naturally occurring isotopes. The mass of
lithium-6 is 6.01512 amu and the mass of lithium-7 is 7.01601
amu. What is the relative abundance of the two isotopes?
*In the early 1970s, Nobel Laureates Whittingham developed the first functional
lithium-ion battery, and in the following decade, Goodenough found a way to
double the battery’s potential. Yoshino made the battery safer by eliminating the
need for pure lithium, a highly reactive metal.
CHEM 6A
56
Isotopes: Are You Wondering …
Why was Carbon-12 selected as the atomic mass standard? The
International Union of Pure and Applied Chemistry (IUPAC) set this standard in
1961, eliminating earlier discrepancies (mostly arising from significant figures!)
that had resulted from the use of oxygen as mass of 16 amu. Oxygen was
originally used as the standard because it forms so many compounds. In
principle, ANY element could be used as a standard for atomic masses.
If you compared samples of diamond, CO2, and CaCO3, would
the proportions of 12C and 13C be different? The percent abundances
of stable isotopes may vary in samples of the element found in nature.
Since their mass are different, do different isotopes of an
element have different chemical reactivity? No, because the
chemical properties of an element are primarily determined by the number of
electrons.
CHEM 6A
57
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
58
How are the Elements Arranged in the
Periodic Table?
*Weighted average
CHEM 6A
59
Early Tables of the Elements
In the 1800s, scientists started looking for ways to classify the
elements.
Early Tables (Mendeleev, 1871) had elements arranged according
to similar properties, but (incorrectly) as a function of atomic mass.
CHEM 6A
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The Modern Periodic Table
Categories of Elements
In the modern periodic table, elements are listed in order of
increasing atomic number, Z, starting at the upper left.
This arrangement places elements with related chemical and
physical properties in groups (columns), of which there are 18.
The elements in periods (rows), of which there are 7, possess
progressively different chemical and physical properties.
CHEM 6A
61
The Modern Periodic Table
Categories of Elements
Period
1
2
3
4
5
6
7
2 elements
8 elements
8 elements
18 elements
18 elements
32 elements
32 elements
All seven periods do not contain the same number of elements.
CHEM 6A
62
The Modern Periodic Table
Main group
Categories of Elements
Main group
The “main group” elements consist of eight groups, labeled 1-2
and 13-18 (or 1A-8A).
CHEM 6A
63
The Modern Periodic Table
Noble Gases
Halogens
Chalcogens
Main group
Pnictogens
Alkaline Earth Metals
Alkali Metals
Main group
Categories of Elements
The “main group” elements consist of eight groups, labeled 1-2
and 13-18. Six of these groups have characteristic names.
CHEM 6A
64
The Modern Periodic Table
Categories of Elements
Transition Metals
In addition to the “main group” elements, there are 10 groups of
transition metals.
CHEM 6A
65
The Modern Periodic Table
Categories of Elements
Lanthanides
Actinides
There are also 14 groups of inner transition metals (called the
lanthanides and actinides) placed at bottom to conserve space.
CHEM 6A
66
The Modern Periodic Table
Categories of Elements
There are also 14 groups of inner transition metals (called the
lanthanides and actinides) placed at bottom to conserve space.
CHEM 6A
67
The Modern Periodic Table
Alternative Versions (Just for Fun!)
Mohd Abubakr from
Microsoft Research in
Hyderabad, India,
CHEM 6A
68
The Modern Periodic Table
Alternative Versions (Just for Fun!)
CHEM 6A
69
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
70
How are the Elements Classified?
*Weighted average
CHEM 6A
71
The Modern Periodic Table
Classification of Elements
Chemical elements are generally classified:
1. as metals, metalloids, or non-metals;
2. by their physical states (solids, liquids, and gases) at STP;
and
3.
CHEM 6A
by their origin, occurrence, and form on Earth.
72
The Modern Periodic Table
Classification of Elements
CHEM 6A
73
The Modern Periodic Table
1. Classification of Elements – Metallic Character
In the bulk, elements are broadly classified as metals or non-metals:
Non-metal
Metal
•
•
•
Luster (or shine)
Malleable and ductile
Good conductor of
heat and electricity
•
•
•
Dull color
Brittle
Poor conductor of heat
and electricity
Semi-metals or metalloids are elements that have characteristics of both
metals and non-metals.
CHEM 6A
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The Modern Periodic Table
1. Classification of Elements – Metallic Character
Elements on the left-hand side of the periodic table are metallic, while
elements on the right-hand side are non-metallic:
17 elements
are non-metals
Only 7 elements
are metalloids
The semi-metals form a zig-zag line of division.
CHEM 6A
75
The Modern Periodic Table
2. Classification of Elements – Physical States
In the bulk, many lighter elements are gases (e.g. H2, N2, O2, F2, Cl2,
noble gases) and heavier elements are solids (e.g. Bi, P4, Te, I2).
What two elements are found in the liquid state at ambient T/P?
CHEM 6A
76
A Thought Experiment
If you were to embark on an “Element Treasure Hunt” about
campus (or home), how many samples of ‘free or uncombined’
elements could you find?
CHEM 6A
77
The Modern Periodic Table
3. Classification of Elements – Origin, Occurrence, Form
•
Following the Big Bang, the universe was comprised mostly of
hydrogen (H) and helium (He).
•
Heavier elements, up to iron (Fe), are formed by fusion of lighter
elements within the core of stars.
•
Supernovae provide the conditions for producing the elements
beyond Fe (Z > 26).
CHEM 6A
78
The Modern Periodic Table
3. Classification of Elements – Origin, Occurrence, Form
Of the 118 chemical elements:
•
94 occur naturally on Earth and 24
are synthesized.
•
80 elements have at least one
stable isotope (Z = 83 and below)
and 38 have exclusively radioactive
isotopes (i.e. their nuclei are
unstable and so they undergo
radioactive decay)
•
Stanford Linear Accelerator (1.8 mi)
Fermilab, Illinios (~ 10 mi2)
4 newest (Z = 113, 115, 117, 118)
were named in June, 2016!
CHEM 6A
79
The Modern Periodic Table
3. Classification of Elements – Origin, Occurrence, Form
Cosmic and whole-Earth abundances are very different:
Cosmic
Stars are powered by
nuclear
reactions,
primarily the fusion of
hydrogen
to
form
helium. [*15% matter of
universe]
CHEM 6A
Crustal
While Fe is the most abundant
element (by mass) on Earth, the
Earth’s crust in made of many
oxides which include SiO2, Al2O3,
FeO, Fe2O3, CaO, MgO, Na2O,
K2O.
Human
Most of the human body is
made of water, H2O;
carbon is the basic unit of
organic molecules.
80
The Modern Periodic Table
3. Classification of Elements – Origin, Occurrence, Form
Given an element’s abundance in a region of the crust, we must next
consider the form in which the element exists on Earth.
Although a few elements occur in an uncombined (native) state, most
are obtained from oxide and sulfide ores (minerals), others from halide
salts, phosphates, carbonates/sulfates, silicates.
CHEM 6A
81
Polling Q: Periodic Facts
Which of the following statements regarding the periodic table is
incorrect?
(A) Reactivity increases down a group.
(B) Hydrogen, in Group 1, is not an alkali metal.
(C) Elements in groups form binary (2 element)
compounds with similar composition.
(D) The largest number of elements are non-metals.
CHEM 6A
82
Polling Q: Periodic Trends
Which of the following will have properties that are very different
from the others?
(A) B
(B) Ba
(C) Be
(D) Bi
(E) Br
CHEM 6A
83
The Modern Periodic Table
Synopsis
Elements are ordered on the Periodic Table by atomic number, Z.
But why does the Table have the arrangement that it does (i.e. 2
elements in the 1st period but 18 elements in the 4th period?)
The position of an element on the Periodic Table is related to the
electronic structure of its atoms.
Let’s explore next what this means …
CHEM 6A
84
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
85
General Chemistry 6A
Energy and Matter: The Big Ideas
Fundamentals: Energy and Matter
A Review of the Big Ideas
What is the scientific approach? What is energy? What is matter?
Exploring Our Universe
Science Practices &
Cross-Cutting Concepts
CHEM 6A
Energy
Matter
2
Fundamentals: Energy and Matter
Your Learning Goals
Can you …
•
Describe the scientific process and the difference
between a hypothesis, theory and law.
•
Differentiate the forms of kinetic and potential
energy, and the total energy of a system.
•
Describe the states of matter.
•
Distinguish between elements, compounds, and
mixtures, as well as physical and chemical
properties and changes.
•
Interpret different representations of matter –
macroscopic, particle, and symbolic.
CHEM 6A
I don’t get it!
I need to re-read,
practice problems,
and seek help.
I kind of get it!
I need to re-read
for clarification,
practice problems,
and seek help if I
have questions.
I got it!
I need to engage in
deliberate practice
to reinforce my
understanding.
I got it! I can teach
it to a friend.
I still need to
practice from time to
time (for retention).
3
The Scientific Approach
How Do We Know?
Key Concepts – Review
CHEM 6A
4
The Dimensions of All Science:
How We Practice It
1. Asking questions and defining problems
2. Developing and using models
3. Planning and carrying out investigations
4. Analyzing and interpreting data
5. Using mathematics and computational thinking
6. Constructing explanations and designing solutions
7. Engaging in argument from evidence
8. Obtaining, evaluating, and communicating information
Discovery – Innovation – Application
CHEM 6A
5
The Dimensions of All Science:
How We Practice It
“The classic view of The Scientific Method is misleading in its
representation of scientific practice.” – Vision Learning
Image: Understanding Science (berkeley.edu)
CHEM 6A
6
The Dimensions of All Science:
How We Practice It
The real process of science is complex, iterative, and can
take many different paths.
https://undsci.berkeley.edu/teaching/guide_to_us.php
CHEM 6A
7
A Scientific Approach
A law is a generalized, analytic statement
about a natural phenomenon.
An hypothesis is a proposed explanation
for a narrow set of phenomena.
CHEM 6A
8
A Scientific Approach
A law is a generalized, analytic statement
about a natural phenomenon.
What?
Why? How?
A theory is a broad explanation of a wide
range of phenomena.
“Scientific truth” is proximate, provisional: it is constantly challenged, refined, and revised.
CHEM 6A
9
Polling Q: Theory vs. Law
Can a theory ever become a law?
(A) Yes
(B) No
(C) I’m not sure
Let’s discuss!
CHEM 6A
10
The Dimensions of All Science:
Cross-Cutting Concepts
1. Patterns
2. Cause and effect: mechanism and explanation
3. Scale, proportion, and quantity
4. Systems and system models
5. Energy and matter: flows, cycles, and conservation
6. Structure and function
7. Stability and change
… And the “Core Ideas” of a Discipline
CHEM 6A
11
The Dimensions of All Science:
Cross-Cutting Concepts
… And the “Core Ideas” of a Discipline
CHEM 6A
12
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
13
What is Energy?
Key Concepts – Review
CHEM 6A
14
Energy
Energy is the “capacity to do work”.
There are two types of energy: kinetic and potential
For any system:
Total Energy = Kinetic Energy + Potential Energy
€
energy associated
with object’s motion
energy associated with object’s
position or composition
The SI unit of Energy is the joule (J). 1 J = 1 kg m2 s-2
CHEM 6A
15
Kinetic Energy, Ek
• Results from (translational) motion of objects
• For an object of mass m traveling at a speed v:
• An object at rest has zero kinetic energy
• Later we will learn that the kinetic energy of atoms and molecules
depends only on temperature.
The SI unit of Energy is the joule (J). 1 J = 1 kg m2 s-2
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16
Potential Energy, Ep
• Results from a force, F, between objects; It is the potential for energy
on account of an objects relative position, d, in a field of force.
Ep = F x d
Gravitational
Electrostatic (or Coulombic)
The SI unit of Energy is the joule (J). 1 J = 1 kg m2 s-2
CHEM 6A
17
Potential Energy, Ep
As we explore matter on microscopic level, we’ll see that electrostatic
forces are responsible for:
1. the attraction of electrons to
the atomic nucleus
2. the bonding of atoms in a
molecule
3. the attraction of oppositely
charged ions in an ionic
compound
4. the attraction between
atoms and/or molecules
that leads to changes of
state
5. the flow of electrical current
CHEM 6A
Electrostatic (or Coulombic)
18
Knowledge Check
When a negative charge and a positive charge interact, the potential
energy is __________ at all finite values of r (or d).
Draw the potential energy curve.
CHEM 6A
19
Law of Conservation of Energy
Ep
Ep > EK
EK > Ep
Heat, Sound
When isolated from external influences, the total energy of an object
or system is constant.
CHEM 6A
20
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
21
What is ‘Matter’ and How is It
Classified?
Key Concepts – Review
CHEM 6A
22
Matter: What is it?
A Particulate View
Matter is anything that _________ and _________.
We classify matter according to its:
1. state or physical form; and
2. composition — the basic “building blocks” or components
(particles) that make it up.
As we progress through CHEM 6A-6C, we’ll explore how the
identity of the building blocks and the type of interactions
between blocks determine the properties of matter.
CHEM 6A
23
The Classification of Matter
1. States or Phases of (Bulk) Matter
In the bulk, all matter may exist in three different physical states.
Macro
View
Solid: fixed volume
and shape (rigid)
Liquid: fixed volume
but variable shape
Gas: expands to fill the
vessel it occupies (fluid)
Micro
View
Phases are affected by both pressure and temperature.
CHEM 6A
24
The Classification of Matter
2. Composition
Physically separable?
Chromatography, crystallization, distillation
NO
Pure Substance
Chemically separable?
YES
Compound
CHEM 6A
NO
Element
25
The Classification of Matter
2. Composition: Pure Substances
Pure substance (an idealization): Is made up of only one component
(building block) and its composition is invariant. i.e. it does not change its
chemical characteristics upon exhaustive attempts at purification.
Atomic interpretation: A pure substance possesses a structure that is
composed of a definite number and kinds of atoms that are connected in a
specific manner.
Pure substances may be either elements or compounds.
CHEM 6A
26
The Classification of Matter
2. Composition: Pure Substances
Element: A substance which cannot be decomposed into simpler
substances by ordinary chemical or physical means (obsolete definition).
Atomic interpretation: An element is a substance that contains only one
kind of atom.
Example: (di)oxygen, O2.
Compound: A substance that can be decomposed into simpler
substances (different elements) by chemical processes.
Atomic interpretation: A compound is a substance that contains atoms of
two or more chemical elements.
Example: Water, H2O
CHEM 6A
27
Chemical Elements
Names and Symbols
All chemical elements have names and a corresponding chemical
symbol, a shorthand (one- or two-letter) notation in which the first letter
is capitalized.
Symbols may be derived from the first letter(s) of an elements common
name or Latin name.
CHEM 6A
28
The Periodic Table of the Elements
“The organizing principles of matter (chemistry) are revealed in
the periodic table”, a tabular format listing all known elements.
CHEM 6A
29
Chemical Compounds
Names and Formulae
Just as elements combine to form chemical compounds, the notation
for a chemical compound – its chemical formula – is derived using
elemental symbols and subscripts to show how many atoms of each
element are present.
C12H22O11
H2O
12 carbon atoms
2 hydrogen atoms
22 hydrogen atoms
1 oxygen atom
11 oxygen atoms
“dihydrogen monoxide”
sucrose
CO2
1 carbon atom
2 oxygen atoms
carbon dioxide
We’ll return to nomenclature rules later this quarter.
CHEM 6A
30
Points to Ponder
The symbol CO represents carbon monoxide, a chemical
compound, but the symbol Co represents cobalt, a chemical
element. Explain how you can tell them apart.
Consider the elements carbon (C), calcium (Ca), and cadmium
(Cd). Can you suggest a possible reason for their chemical
symbols?
CHEM 6A
31
The Classification of Matter
2. Composition
Physically separable?
Chromatography, crystallization, distillation
YES
Mixture
Pure Substance
Uniform properties?
Chemically separable?
Optical microscopy
YES
Homogeneous
CHEM 6A
NO
NO
Heterogeneous
YES
Compound
NO
Element
32
The Classification of Matter
2. Composition: Mixtures vs. Pure Substances
Mixture: A blend of two or more substances, each of which retains its
chemical identity.
Examples:
Air is a homogenous mixture of
several
gases,
including
nitrogen, N2 (78%), oxygen, O2
(21%) and argon, Ar (0.93%).
Granite is a heterogeneous
mixture of solid SiO2, Al2O3,
Na2O, FeO and many other
minerals.
We’ll learn more about mixtures in CHEM 6B.
CHEM 6A
33
What Properties Does Matter
Have? What Changes Does It
Undergo?
Key Concepts – Review
CHEM 6A
34
A Thought DEMO: Dry Ice
Imagine we added dry ice (solid carbon dioxide) to an open container
with and without water.
What might you expect to see?
What do you think is happening? What is your reasoning?
Can you represent the changes using all the dimensions?
CHEM 6A
35
Changes in Matter
Physical vs. Chemical Changes
•
Matter can undergo two types of changes – physical or chemical –
that are distinguished by whether or not its composition remains
constant or changes, respectively.
•
During these transformations, mass and energy are conserved.
•
We often represent a change using a chemical equation, in which
substances are listed by their symbols or formulae, along with their
physical states:
Starting substance (reactants) ® Ending substance (products)
.
Physical states: (g) – gas; (l) – liquid; (s) – solid
*(aq) – denotes a solution of a solute dissolved in H2O, the solvent
CHEM 6A
36
Physical Changes
Chemical Composition Unaltered
Example: Dry ice sublimes
CO2(s) ® CO2(g)
CHEM 6A
37
Physical Changes
A change of phase or state is the conversion of a substance from
one physical state to another.
Increase Temperature
Decrease Pressure
Gas
Deposition
Decrease Temperature
Increase Pressure
Condensation
Sublimation
Vaporization
Freezing
Solid
CHEM 6A
Melting (Fusion)
Liquid
38
Chemical Changes (Reactions)
Chemical Composition Altered
Example: CO2 dissolves and reacts with H2O to form carbonic acid
CO2(g) + H2O(l) ® H2CO3(aq)
CHEM 6A
39
Properties of Matter
A chemical property is one that a substance displays only by changing
its composition through a chemical reaction.
Examples: flammability, acidity, toxicity, corrosiveness
A physical property is a characteristic that we can observe or measure
without changing the chemical identity (composition) of the substance.
Examples: melting point, hardness, color, density, mass
Physical quantity = numerical value x unit
The Système International (SI) defines seven base units in terms of
which all physical quantities can be expressed.
CHEM 6A
40
Physical
Properties
Water
H2O
Carbon Dioxide
CO2
Density
999 kg/m3
1.977 kg/m3
Melting Pt
0°C
-78°C (sublimes)
Boiling Pt
100°C
—
Chemical
Properties
Water
H2O
Carbon Dioxide
CO2
Flammability
Does not burn
Does not burn
Acidity/Basicity
Neutral
Acidic
Color, form
Odor
CHEM 6A
41
Quick Write
Write a one-sentence summary of this section.
Check the learning goals. What question(s) do you have?
CHEM 6A
42
Interconverting Energy and Matter
“The World’s Most Famous Equation”
Albert Einstein’s famous equation shows that anything having
mass has an equivalent amount of energy, and vice versa:
A small amount of mass is the same as a very large amount of energy. The
proportionality constant is the square of the speed of light, (3.0 x 108 m/s)2.
Only in nuclear reactions are mass-energy interconversions
detectable. Both energy and mass are separately conserved in
ordinary chemical reactions and physical changes.
CHEM 6A
43
measured numerical quantities
are expressed on a
scale
defined by the
magnitude
units of
of its
intervals
measure
that can be related to
a small number of fundamental
the most important
of which in
science are the
SI units
which consist of
7 SI Base Units
“companion”
units
dimensions
the most
important
being
which can be
deduced by
decimal prefixes
derived units
dimensional analysis
mass
length
time
electric charge
temperature
which is
useful to
show the relationship
between different units
implicitly tell how to
calculate a quantity
provide a check on
numeric calculations
Stephen Lower
Stephen Lower
Free Energy
is not
is a
“energy”
state function
that expresses the
spontaniety of a
chemical process
quantity of non-PV
work that a system
can perform
in terms of
enthalpy and
entropy change
of the system
under conditions of
constant
Tamd v
(Helmholtz)
free energy)
constant
T and P
(Gibbs
free energy)
known as the
for a chemical reaction
system is based on
Gibbs function
G = H-TS
whose
also expresses
the
differences in
standard free energies
of formation of
products and reactants
Temperature dependence
is revealed by
in which
“escaping tendency”
of a reaction component
delta-G
in terms of
plots showing Delta-H
and T-Delta S
as functions of T
means
pressure
of a gas
showing that the
reaction is in equilibrium
(Delta-G = 0) when
reaction proceeds
to the right
= 0 means
phase change
T = Delta-H/Delta-S
reaction proceeds
to the left
reaction is at
equilibrium