Chapters 7 and 8
1. 1980 #9
a. Write the ground-state electron configuration for an arsenic atom, showing the number of electrons
in each subshell.
b. Give one permissible set of four quantum numbers for each of the outermost electrons in a single
As atom when it is in its ground state.
c. Is an isolated arsenic atom in the ground state paramagnetic or diamagnetic? Explain briefly.
d. Explain how the electron configuration of the arsenic atom in the ground state is consistent with the
existence of the following known compounds: Na3As, AsCl3, and AsF5.
2. 1982 #6
The values of the first three ionization energies (I1, I2, I3) for magnesium and argon [in kJ/mole] are as
follows:
I1
I2
I3
Mg
735
1443
7730
Ar
1525
2665
3945
a. Give the electronic configuration of Mg and Ar.
b. In terms of these configurations, explain why the values of the first and second ionization energies
of Mg are significantly lower than the values for Ar, whereas the third ionization energy of Mg is
much larger than the third ionization energy Ar.
c. If a sample of Ar in one container and a sample of Mg in another container are each heated and
chlorine is passed in to each container, what compounds, if any, will be formed? Explain in terms of
the electronic configuration given in part (a).
d. Element Q has the following first three ionization energies [in kJ/mole]:
Q
I1
I2
I3
496
4568
6920
What is the formula for the most likely compound of element Q with chlorine? Explain the choice of
formula on the basis of the ionization energies.
3. 1985 #5 b-c
Properties of the chemical elements often show regular variations with respect to their positions in the
periodic table.
b. How does the oxidizing strength of the halogen elements vary down the group? Account for this
trend.
c. How does the reducing strength of the alkali metals vary down the group? Account for this trend.
4. 1987 #5
Use the details of modern atomic theory to explain each of the following experimental observations.
a. Within a family such as the alkali metals, the ionic radius increases as the atomic number
increases.
b. The radius of the chlorine atom is smaller than the radius of the chloride ion, Cl¯. (Radii: Cl atom =
0.99 Å; Cl= ion = 1.81 Å)
c. The first ionization energy of aluminum is lower than the first ionization energy of magnesium. (First
ionization energies: 12Mg = 7.6 ev, 13Al = 6.0 ev)
d. For magnesium, the difference between the second and third ionization energies is much larger
than the difference between the first and second ionization energies. (Ionization energies, in
electron-volts, for Mg: 1st = 7.6, 2nd = 14, 3rd = 80)
5. 1987 #9
Two important concepts that relate to the behavior of electrons in atomic system are the Heisenberg
uncertainty principle and the wave-particle duality of matter.
a. State the Heisenberg uncertainty principle as it relates to determining the position and momentum
of an object.
b. What aspect of the Bohr theory of the atom is considered unsatisfactory as a result of the
Heisenberg uncertainty principle?
c. Explain why the uncertainty principle or the wave nature of particles is not significant when
describing the behavior of macroscopic objects, but is very significant when describing the behavior
of electrons.
first ionization energy
(kJ/mol)
6. 1990 #6
2500
2000
1500
1000
500
0
3
5
7
9
11
atomic number
The diagram shows the first ionization energies for the elements from Li to Ne. Briefly (in one to three
sentences) explain each of the following in terms of atomic structure.
a. In general, there is an increase in the first ionization energy from Li to Ne.
b. The first ionization energy of B is lower than that of Be.
c. The first ionization energy of O is lower than that of N.
d. Predict how the first ionization energy of Na compares to those of Li and of Ne. Explain.
7. 1993 #6
Account for each of the following in terms of principles of atomic structure, including the number,
properties, and arrangements of subatomic particles.
a. The second ionization energy of sodium is about three times greater than the second ionization
energy of magnesium.
b. The difference between the atomic radii of Na and K is relatively large compared to the difference
between the atomic radii of Rb and Cs.
c. A sample of solid nickel chloride is attracted into a magnetic field, whereas a sample of solid zinc
chloride is not.
d. Phosphorus forms the fluorides PF3 and PF5, whereas nitrogen forms only NF3.
8. 1994 #9
Use principle of atomic structure and/or chemical bonding to answer of each of the following.
a. The radius of the Ca atom is 0.197 nanometer; the radius of the Ca 2+ ion is 0.099 nanometer.
Account for this difference.
b. The lattice energy of CaO(s) is -3,460 kilojoules per mole; the lattice energy for K2O(s) is -2,240
kilojoules per mole. Account for this difference.
1st ionization energy (kJ/mol)
2nd ionization energy (kJ/mol)
K
419
3050
Ca
590
1140
c.
Explain the difference between Ca and K in regard to:
their first ionization energies.
their second ionization energies.
d. The first ionization energy of Mg is 738 kilojoules per mole and that of Al is 578 kilojoules per mole.
Account for this difference.
i.
ii.
9. 1997 #6
Explain each of the following observations using principles of atomic structure and/or bonding.
a. Potassium has a lower first-ionization energy than lithium.
b. The ionic radius of N3¯ is larger than that of O2¯.
c. A calcium atom is larger than a zinc atom.
d. Boron has a lower first-ionization energy than beryllium.
10. 1999 #2
Answer the following questions regarding light and its interactions with molecules, atoms, and ions.
a. The longest wavelength of light with enough energy to break the Cl-Cl bond in Cl2(g) is 495 nm.
i.
Calculate the frequency, in s-1, of the light.
ii.
Calculate the energy, in J, of a photon of the light.
Calculate the minimum energy, in kJ mol-1, of the Cl-Cl bond.
b. A certain line in the spectrum of atomic hydrogen is associated with the electronic transition in the H
atom from the sixth energy level (n=6) to the second energy level (n=2).
i.
Indicate whether the H atom emits energy or whether it absorbs energy during the transition.
Justify your answer.
ii.
Calculate the wavelength, in nm, of the radiation associated with the spectral line.
iii.
Account for the observation that the amount of energy associated with the same electronic
transition (n=6 to n=2) in the He+ ion is greater than that associated with the corresponding
transition in the H atom.
iii.
11. 2000#7
Answer the following questions about the element selenium, Se (atomic number 34).
a. Samples of natural selenium contain six stable isotopes. In terms of atomic structure, explain what
these isotopes have in common, and how they differ.
b. Write the complete electron configuration (e.g., 1s22s2… etc.) for a selenium atom in the ground
state. Indicate the number of unpaired electrons in the ground-state atom, and explain your
reasoning.
c. In terms of atomic structure, explain why the first ionization energy of selenium is
i.
Less than that of bromine (atomic number 35), and
ii.
Greater than that of tellurium (atomic number 52)
d. Selenium reacts with fluorine to form SeF4. Draw the complete Lewis electron-dot structure.
Indicate whether the molecule is polar or nonpolar, and justify your answer.
12. 2003 B #7
Account for the following observations using principles of atomic structure and/or chemical bonding. In
each part, your answer must include specific information about both substances.
a. The Ca2+ and Cl- ions are isoelectronic, but their radii are not the same. Which ion has the larger
radius? Explain.
b. Carbon and lead are in the same group of elements, but carbon is classified as a nonmetal and
lead is classified as a metal.
c. Compounds containing Kr have been synthesized, but there are no known compounds that contain
He.
d. The first ionization energy of Be is 900 kJ mol-1, but the first ionization energy of B is 800 kJ mol-1.
13. 2006 #8
Suppose that a stable element with atomic number 119, symbol Q, has been discovered.
a. Write the ground-state electron configuration for Q, showing only the valence shell electrons.
b. Would Q be a metal or a nonmetal? Explain in terms of electron configuration.
c. On the basis of periodic trends, would Q have the largest atomic radius in its group or would it have
the smallest? Explain in terms of electronic structure.
d. What would be the most likely charge of the Q ion in stable ionic compounds?
e. Write a balanced equation that would represent the reaction of Q with water.
f. Assume that Q reacts to form a carbonate compound.
i.
Write the formula for the compound formed between Q and the carbonate ion, CO32-.
ii.
Predict whether or not the compound would be soluble in water. Explain your reasoning.
14. 2006B #7a, c, d
Account for each of the following observations in terms of atomic theory and/or quantum theory.
a. Atomic size decreases from Na to Cl in the periodic table.
c. The first ionization energy of K is less than that of Na.
d. Each element displays a unique gas-phase emission spectrum.
15. 2007 B #2
Answer the following problems about gases.
a. The average atomic mass of naturally occurring neon is 20.18 amu. There are two common
isotopes of naturally occurring neon as indicated in the table below.
Isotope
Mass (amu)
Ne – 20
19.99
Ne – 22
21.99
i.
Using the information above, calculate the percent abundance of each isotope.
ii.
Calculate the number of Ne – 22 atoms in 12.55 g sample of naturally occurring neon.
b. A major line in the emission spectrum of neon corresponds to a frequency of 4.34x10 14 s-1.
Calculate the wavelength, in nanometers, of light that corresponds to this line.
c. In the upper atmosphere, ozone molecules decompose as they absorb ultraviolet (UV) radiation, as
shown by the equation below. Ozone serves to block harmful ultraviolet radiation that comes from
the Sun.
 O2 (g) + O (g)
O3 (g) 
A molecule of O3 (g) absorbs a photon with a frequency of 1.00x1015 s-1.
i.
How much energy, in joules, does the O3 (g) molecule absorb per photon?
ii.
The minimum energy needed to break an oxygen – oxygen bond in ozone is 387 kJ mol-1.
Does a photon with a frequency of 1.00x10 15 s-1 have enough energy to break this bond?
Support your answer with a calculation.
UV
16. 2007 B #6
The table below shows the first three ionization energies for atoms of four elements from the third
period of the periodic table. The elements are numbered randomly. Use the information in the table to
answer the following questions.
Element 1
Element 2
Element 3
Element 4
a.
b.
c.
d.
e.
f.
First
Ionization Energy
(kJ mol-1)
1251
496
738
1000
Second
Ionization Energy
(kJ mol-1)
2300
4560
1450
2250
Third
Ionization Energy
(kJ mol-1)
3820
6910
7730
3360
Which element is most metallic in character? Explain your reasoning.
Identify element 3. Explain your reasoning.
Write the complete electron configuration for an atom of element 3.
What is the expected oxidation state for the most common ion of element 2?
What is the chemical symbol for element 2?
A neutral atom of which of the four elements has the smallest radius?