AP Chemistry
Unit 2: Atoms & Bonding
Packet #4 – Due Monday, October 6th
Chemist: ________________________
Date: ________________________
9/30
2.3
10/7
10/1
AP C
9/29
2.1 & 2.2
10/6
Packet 4 Due
Quiz 4
9/29
2.1
10/6
Packet 4 Due
Quiz 4
9/30
AP D
Schedule
10/7
10/8
10/2
2.4
10/9
10/3
2.5
10/10
10/1
2.2
10/8
10/2
2.3 & 2.4
10/9
10/3
2.5
10/10
Checklist
 2.1 – Atomic Structure
o CW 2.1: Presentation Intro & Rubric +
Presentation Notes
o Notes 2.1
o HW 2.1 on Mastering Chemistry
 2.2 – Bonding Models & Coulomb’s Law
o CW 2.2
o Notes 2.2
o HW 2.2 on Mastering Chemistry
 2.3 – Electron Configuration
o CW 2.3
o Notes 2.3
o HW 2.3 on Mastering Chemistry
 2.4 – PES
o Notes 2.4
o HW 2.4 on Mastering Chemistry
 2.5 – Mass Spec & Isotope Abundance
o CW 2.5
o Notes 2.5
o HW 2.5 on Mastering Chemistry
Learning Objectives
1.5
1.6
1.7
1.12
1.13
1.14
The student is able to explain the distribution of electrons in an atom or ion based upon data.
The student is able to analyze data relating to electron energies for patterns and relationships.
The student is able to describe the electronic structure of the atom, using PES data, ionization energy data, and/or
Coulomb’s Law to construct explanations of how the energies of electrons within shells in atoms vary.
The student is able to explain why a given set of data suggests, or does not suggest, the need to refine the atomic model
from a classical shell model with the quantum mechanical model.
Given information about a particular model of the atom, the student is able to determine if the model is consistent with
specified evidence.
The student is able to use data from mass spectrometry to identify the elements and the masses of individual atoms of a
specific element.
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Classwork 2.1 – Atomic Structure
AP Learning Objectives related to the development of the atomic model:
1.12 The student is able to explain why a given set of data suggests, or does not suggest, the need
to refine the atomic model from a classical shell model with the quantum mechanical model.
1.13 Given information about a particular model of the atom, the student is able to determine if the
model is consistent with specified evidence.
You will need to be able to defend your choice of atomic structure based on evidence, not memorize the
evidence for each shift in the atomic model. In order to practice using evidence to support a shift in the
atomic model, you will give a 3-minute presentation on an assigned change in the atomic model. You have 30
min class to work on this presentation. When you are finished, your slides must be added to the class notes.
Each presentation must include:
 A claim about the structure of the atom, provided by Ms. Haines
 Evidence to support the new claim and cited from textbooks or web resources
 Historical context & information about the significance of the discovery. This may include any details
you deem relevant. Suggestions include:
o Date
o Scientists involved, their affiliated university/partners, awards received
o Acceptance by or impact on the scientific community
o Other historical information to put the discovery into context
o Future implications of this discovery
Grading Information:
This will be graded as a classwork assignment, worth 10 points. You will be graded on content (4 pts), slide
organization (2 pts), presentation skills (2 pts), and ability to answer questions (2 pts).
During presentations, please take notes in the space below:
Discovery of the Atom
Claim: Atoms are the smallest units of matter and con be combined in set ratios to form compounds.
Evidence:
Historical/Contextual Information:
2
Discovery of the Electron
Claim: Negatively charged particles can be removed from an atom. These negatively charged particles
will be called “electrons.”
Evidence:
Historical/Contextual Information:
Discovery of the Charge to Mass Ratio on an Electron.
Claim: Electrons have a charge to mass ratio of 1.76 x 108 Coulombs per gram.
Evidence:
Historical/Contextual Information:
Discovery of the Charge on an Electron
Claim: Electrons have a charge of 1.6 x 10-19 Coulombs.
Evidence:
Historical/Contextual Information:
3
Discovery of the Proton
Claim: Small positively charged particles reside in the center of an atom. These positive particles are
called “protons.”
Evidence:
Historical/Contextual Information:
Discovery of the Neutron
Claim: Small uncharged particles reside in the center of an atom. These neutral particles are called
“neutrons.”
Evidence:
Historical/Contextual Information:
4
Notes 2.1 – Current Atomic Structure
 Proton –
 Neutron –
 Electron –
 Atomic Number –
 Atomic Mass –
 Mass Number –
 Isotope Symbol –
 Isotope Name –
Determining #:
 # of protons –
 # of neutrons –
 # of electrons –
Sample Problems (assume all atoms are neutral)
Isotope Name
Isotope Symbol
Mass Number
Protons
Electrons
Neutrons
Carbon – 14
15
150
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HW 2.1
Problems I want to review in class from HW 2.1
5
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Classwork 2.2
Procedure
1. Place one magnetic marble on top of the grey circle shown at the origin of your graph below. One
person should hold this marble in place so that it will NEVER move.
2. Place the second magnetic marble on the x-axis of your graph so that the center of the marble is at 9
cm.
3. Slowly move the second magnetic marble closer to the origin, noting any attractive or repulsive forces
you feel by making marks above (repulsion) or below (attraction) the x-axis. Marks farther away from
the x-axis mean that you feel the force of attraction/repulsion more strongly.
Data
Analysis
After taking your data, describe what you would expect the marbles to do next in the scenarios given below:
1. If the marbles are far apart…
2. If the marbles are very close but not touching…
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3.
The marbles are so close that the outside of the marble is slightly elastically deformed, like this:
Original Marble
Slightly Elastically
Deformed Marble
Bond Potential Energy (Cal)
Model 1: Bond Potential Energy vs. Internuclear Distance Graph
1. In the graph shown above R indicates the internuclear distance. At what distance, measured in Angstroms (Å),
will the bond have the lowest energy?
2. In your own words, explain what happens if the bond length is shorter than the length listed in problem 1.
3. How much energy is needed to break the bond shown above?
4. What is responsible for the attraction that creates chemical bonds?
5. Draw a line on the graph above that represents a different chemical bond that has the same preferred distance
of separation, but requires less energy to break.
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Notes 2.2 – Bonding Types
 Chemical Bond –
o
Ionic Bond –
o
Metallic Bond –
o
Covalent Bond –
HW 2.2
Problems I want to review in class from HW 2.2
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Classwork 2.3
Model 1: Electron Configuration for the First 10 Elements on the Periodic Table
H
He
Li
Be
B
1s1
1s2
1s22s1
1s22s2
1s22s22p1
C
N
O
F
Ne
1s22s22p3
1s22s22p4
1s22s22p5
1s22s22p6
Questions
1. What is the electron configuration for Helium? Copy it in the space below.
2. What is the electron configuration for Neon? Copy it in the space below.
3. As the atomic number increases, what patterns do you notice in the electron configurations?
4. Fill in the electron configurations for carbon and fluorine in the chart above.
5. Write a possible electron configuration for sodium, Na.
STOP! Raise your hand and have Ms. Haines check your work up to this point.
6. Revise your answer to problem 5 using the chart above.
7. What is the electron configuration for sulfur, S, referencing the table above?
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Model 2: More Electron Configurations
Na
1s22s22p63s1
[Ne]3s1
P
1s22s22p63s23p3
[Ne]3s23p3
Ar
1s22s22p63s23p6
[Ne]3s23p6
Cu
1s22s22p63s23p64s13d10
[Ar]4s13d10
Ga
1s22s22p63s23p64s23d104p1
[Ar]4s23d104p1
Rn
1s22s22p63s23p64s23d104p65s24d6
[Kr]5s24d6
8. What are the two ways to write an electron configuration for Na?
9. Why do you think chemists have two methods for writing electron configurations?
10. Write an electron configuration and the shorthand configuration for sulfur.
11. What is the maximum number of electrons allowed in…
a. An s orbital?
b. A p orbital?
c. A d orbital?
d. An f orbital?
Valence Electrons: the outermost electrons of an atom; those that occupy orbitals not occupied in the nearest
noble-gas element of lower atomic number.
Valence Orbitals: Orbitals that contain the outer-shell electrons of an atom.
Core Electrons: The electrons that are not in the outermost shell of an atom.
12. In Model 2 above, put a box around the portion of the electron configurations that represents the core
electrons. Underline the portion of the electron configuration that represents the valence electrons.
13. What is the relationship between valence/core electrons and the short-hand electron configuration?
14. Identify the element associated with each of the following electron configurations:
a. 1s22s22p63s23p1
b. 1s22s22p63s23p64s2
c. 1s22s22p63s23p64s23d8
d. [Ne]3s23p3
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Model 3: Excited State vs. Ground State Electron Configurations
Ground State
Excited State
H
1s1
2s1
Na
1s22s22p63s1
1s22s22p63p1
Zn
1s22s22p63s23p64s23d10
1s22s22p63s23p64s13d105s1
1. Define the following:
Ground State:
Excited State:
2. If you were given an electron configuration and you were asked whether it represented a ground-state or
excited-state electron, how would you be able to tell?
3. Write a ground state and excited state electron configuration for the carbon atom shown below. Note which
one is excited and which one is ground state.
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Notes 2.3 – Electron Configuration
 Electron Configuration
 Hund’s Rule
 Aufbau Principle
Electron
Shell
n=1
Write electron configurations for the following elements:
n=2
Oxygen: __________________________________
Max e—
Electron
Subshell
s
s
p
s
Argon: __________________________________
n=3
p
d
Magnesium: __________________________________
s
Chlorine: __________________________________
n=4
p
d
f
Oxygen
Argon
Magnesium
HW 2.3
Problems I want to review in class from HW 2.3
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Chlorine
Max e—
Classwork 2.4 - PES
 Ionization energy –
1. Label the following locations on this graph:
A. “Ground state” for an electron orbiting the nucleus.
B. Point at which an electron feels more repulsion from neighboring electrons than attraction by the nucleus.
C. Point at which an electron feels equal repulsion from neighboring electrons and attraction by the nucleus.
D. Point at which an electron is far enough away from the nucleus that it feels little to no attraction.
2. Photoelectron spectroscopy is the process of hitting a sample of gas of a single element with photons of varying
energy. Energy is absorbed by the sample. If a photon with enough energy strikes the surface to ionize, it can
transfer its energy to electrons that then leave the sample. The electrons’ speed is detected by an analyzer. The
ionization energy can then be determined using:
Energy of Initial Photon = Ionization Energy + Kinetic Energy of Emitted Electron
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3. Examine the hypothetical atom below. What is the ionization energy required to remove this electron from the
atom?
4. When this photoelectron spectroscopy (PES) data is collected, it is transformed into a graph that looks
something like this:
A. What determines the position of each peak along the horizontal axis in a PES?
B. What determines the height of each peak in a PES?
C. Explain why it is not possible to determine the number of electrons in an individual hypothetical atom from
the PES in the graph above.
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5. Examine this more complex atom and the associated photoelectron spectrum for neon, Ne. Why do you think
there are multiple peaks in the PES?
A. What is unusual about the graph?
B. Does the peak at 84.0 MJ/mol indicate that it takes more or less energy to remove those electrons than the
peak at 2.08 MJ/mol?
C. Would you expect the electrons at 84.0 MJ/mol to be closer to the nucleus or farther from the nucleus than
the electrons at 2.08 MJ/mol?
D. Rank the peaks in order of INCREASING number of electrons. If two peaks have the same number of
electrons, indicate that with an “=” sign.
E. Write the electron configuration for neon below.
F. Why do you think there are multiple peaks in the PES? (HINT: examine the electron configuration)
G. How many electrons are represented by the shorter peak?
H. How many electrons are represented by the taller peak?
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Notes 2.4 – Photoelectron Spectroscopy
What element do these spectra represent?
HW 2.4
Problems I want to review in class from HW 2.4
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Classwork 2.5 – Mass Spectrometry
Model 1: Mass Spectrometry
Red Beam (A)
O2 → O+ + O2+
Negative Plate
magnet
Black Beam (B)
C D E
+
F G H
2+
When oxygen gas is released from a mass spectrometer, two different ions are formed: O and O . Three isotopes of
oxygen are detected: 16O, 17O and 18O.
1. Which beam of ions (A or B) represents the O+2 ion? Explain your answer.
2. Which TWO beams (C thru H) represent the O-18 isotope? Explain.
3. According to the diagram above, which isotope of oxygen is the most abundant? Explain.
Summary:
 The job of a Mass Spectrometer is to separate out different _____________________ of a given element by
applying an electromagnetic field.
 Atoms that bend toward the negative plate more easily have a _____________________ charge. They also have
a ____________________ mass because it takes less energy to change their direction of motion.
 Atoms that have a more difficult time bending toward the negative place have a _____________________
charge and __________________ mass because it takes more energy to change their direction of motion.
 The isotope with the greatest abundance will appear as a darker line.
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Model 2: Mass Spectrometry Graphs
The experiment shown in Model 1 would produce a graph that looks like this:
It is difficult to see, but there are three peaks shown here. Each peak shows the relative abundance of each mass.
6. What are the three mass values found for oxygen? Write the isotope symbols.
7. Which isotope is most abundant? Write its symbol and explain how you know.
6. Using the masses of the elements shown and the relative abundance of the different isotopes, identify each
element from the mass spectrum given below.
Mass Spectrum
Element Identity &
Reasoning
A. Lithium
B. Beryllium
C. Boron
D. Carbon
Rationale:
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A.
B.
C.
D.
Sulfur
Chlorine
Bromine
Krypton
Rationale:
A.
B.
C.
D.
Selenium
Gold
Mercury
Bromine
Rationale:
A.
B.
C.
D.
Copper
Zinc
Gadolinium
Europium
Rationale:
This is a more
complicated spectrum of
Tellurium. There are
more lines because Te
has many isotopes.
Mass spectra are not
limited to two peaks!
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Notes 2.5 – Isotope Abundance
 Abundance –
 Weighted average formula –
𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐴𝑡𝑜𝑚𝑖𝑐 𝑀𝑎𝑠𝑠
(𝑝𝑒𝑟𝑐𝑒𝑛𝑡 𝐴 × 𝑚𝑎𝑠𝑠 𝐴) + (𝑝𝑒𝑟𝑐𝑒𝑛𝑡 𝐵 × 𝑚𝑎𝑠𝑠 𝐵) + ⋯ + (𝑝𝑒𝑟𝑐𝑒𝑛𝑡 𝑁 × 𝑚𝑎𝑠𝑠 𝑁)
=
𝑡𝑜𝑡𝑎𝑙 𝑝𝑒𝑟𝑐𝑒𝑛𝑡
Sample Problems
1. If lithium is 5.9% lithium-6 and 94.1% lithium 7, what is the average atomic mass of lithium?
2. If chlorine is 77% chlorine-35 and 23% chlorine-37, what is the average atomic mass of chlorine?
3. Bromine’s average atomic mass is 79.90. Only two isotopes are found in nature: bromine-79 and bromine-81.
What is the percent abundance of each one?
HW 2.5
Problems I want to review in class from HW 2.5
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