Answer Key
Chapter 5
Practice Problems
1. 4.741014 Hz
2. 6.251010 m; (0.625 nm)
3. 3.05 m
4. 3.331013 J
5. Ephoton (violet)  4.51019 J
Ephoton (red)  2.81019 J
Edifference  1.71019 J
6. First calculate the frequency of the light.
  6.121015 Hz
Ephoton  4.061018 J
7. Bohr’s model showed that electrons move in circular orbits around
the nucleus. The electrons have the energies associated with those
orbits.
8. The electron is moving from an orbital of higher energy to an orbital
of lower energy.
9. The second principal energy level can hold eight electrons (two in
the 2s sublevel and six more in the 2p sublevel). The third principal
energy level can hold eighteen electrons (two in the 3s sublevel, six
in the 3p sublevel, and ten in the 3d sublevel). The difference is due
to the fact that the larger third principal energy level has one more
available energy sublevel.
10. The sublevels are written in order of increasing energy.
11. The number of electrons is indicated as a superscript integer to the
right of the sublevel.
12. a. 1s22s22p63s23p4
c. 1s22s22p63s23p64s23d104p5
2 2
6 2
6 2
b. 1s 2s 2p 3s 3p 4s
d. 1s22s22p63s2
Answer Key (continued)
13. a.
b.
c.
d.
e.
14. a.
[He]2s22p5
[Ne]3s23p3
[Ar]4s2
[Ar]4s23d7
[Ar]4s23d104p4
c.
f.
g.
h.
i.
j.
e.
[Kr]5s24d5
[Kr]5s24d105p5
[Xe]6s24f11
[Xe]6s24f145d7
[Rn]7s2
g.
b.
d.
f.
h.
15. eight dots surrounding the symbol for the element
16. Student responses may include any of the group 15 elements:
nitrogen, phosphorus, arsenic, antimony, and bismuth.
Chapter 5 Review
17. The equation c   relates the speed, wavelength, and frequency of
an electromagnetic wave. The frequency of a given wave cannot
change; wave speed and wavelength are directly related. Therefore,
the wavelength will decrease as speed decreases.
18. Light striking a metal plate dislodges electrons from the plate.
Einstein concluded that light could act not only as a wave, but also
as a stream of particles, called photons.
19. Energy increases as frequency increases. Energy decreases as
wavelength increases (because frequency decreases).
20. According to Bohr’s model, an atom’s electrons travel around the
nucleus in circular orbits, each of which has a specific energy value.
Electrons can jump only from one allowable orbit to another.
Therefore, electrons can increase or decrease in energy only by
certain amounts. These amounts correspond to the frequencies
(colors) of the light seen in the atomic emission spectrum.
21. Three energy sublevels are available—s, p, and d. An s sublevel can
hold two electrons; a p sublevel can hold six electrons; and a d
sublevel can hold ten electrons.
Answer Key (continued)
22. In the modern model of the atom, electrons are not in specific orbits.
Instead, they are in regions of space in which there is a high
probability of finding electrons of a certain energy.
23. a. fluorine
e. rhodium
b. manganese
f. polonium
c. germanium
g. sulfur
d. sodium
h. cadmium
24. The dots represent the electrons in the highest principal energy level
of the atom. These electrons are called valence electrons, and they
determine many of the chemical properties of an element.
25. Student responses may include helium and any of the group 2
elements: beryllium, magnesium, calcium, strontium, barium, and
radium.