AP Chemistry
Unit 2 Review Guide Key
1. A photon is a quantity (quanta) of energy. It can be in the visible spectrum or not. Photon energy is directly
related to frequency and inversely related to wavelength.
ℎ
ℎ
2. 𝜆 =
=
= 9.8𝑥10−42 𝑚
8
𝑚𝑣
0.45𝑘𝑔∙1.5𝑥10 𝑚/𝑠
3. It determined the probability of finding an electron within a specific region of space surrounding the nucleus.
4. One cannot calculate both the position and momentum of an electron simultaneously. If you know the position
with a high degree of certainty, then you wouldn’t know much about the momentum of an electron.
5. 2n2 = 2(4)2=32
6. It tells how many electrons are in which specific orbital. You can tell whether the orbital is full or half-full.
7. Hund’s rule. Since electrons are negatively charged they repel into separate orbitals if possible.
8. Shows the valence electrons, the e- in the outermost energy level. These electrons are used in bonding.
9. They are all filling up with electrons into the same principle energy level.
10. Same number of valence e-.
11. Bohr proposed spherical orbits at varying distances from the nucleus. QM predicts probability clouds based on
schrodinger’s wave equation.
12. Properties repeat because the pattern of valence electrons repeats. Group 1 metals all have one valence e- and
therefore, similar properties.
13. a) F
c) F
b) I
d) F
14. No definite boundary at the “edge” of the electron cloud. Use the covalent radius, which is half the distance
between the nuclei of two covalently bonded atoms.
15. d-block elements. Groups 3-12 the transition metals.
16. Shielding electrons are the electrons between the valence electrons and the nucleus of an atom. They interfere
with the coulombic attraction between the nucleus and the valence e-.
17. Coulombs law answers this question. As the distance between the nucleus and the shielding e- decreases the
force required to remove them increases. You could also say that the energy (E) required to remove the eincreases.
18. It would be on the left side. Metals are found on the left side and they lose e- to achieve an octet of electrons.
19. Electrons occupy the lowest energy level possible. Also, e- occupy lowest orbitals possible: s, p, d, f, etc.
20. Only two electrons per orbital are allowed.
21. Again Coulomb’s Law. As electrons are removed from the same sublevel there is less e- to e- repulsion and
there is an increasing force of attraction from the nucleus that is pulling upon the same sublevel. More protons
attracting to fewer electrons. Also, as e- are removed to empty out an energy level that means any additional ewould have to be removed from the next closest energy which would be more strongly attracted to the nucleus.
22. Sodium because it has one less proton pulling on the electrons. Coulomb’s law.
23. The 4s-sublevel is lower in energy than the 3d and according to the Aufbau principle lowest energy sublevels fill
first.
24.
Sybmol
Lewis-dot
diagram
Electron configuration
(use noble gas shortcut)
[He]2s22p6
Ne
[Ar]4s13d10
Cu
[Ne]3s23p6
S2[Rn]7s24f4
U
[Ne]3s23p6
Ca2+
25. Atomic radius generally decreases across a period. Effective nuclear charge increases left to right, the result is
that ever increasing numbers of protons are pulling on the same energy shell.
26. Radius increases from top to bottom of group, because energy levels are added. Again think of Coulomb’s law as
“d” increases E decreases meaning e- are easier to remove and held onto with less force of attraction.
27. IE increases because the Zeff is increasing making it more difficult to ionized electrons.
28. IE decreases from top to bottom of a group because distance from nucleus to valence shell is increasing making it
easier to remove electrons. Again Coulombs law.
29. Coulomb’s Law. As “d” increases the energy required to ionize decreases. 𝐸 ≈
𝑄1 𝑄2
𝑑
30. Metal ions have given away their valence electrons found on outermost energy level, thereby decreasing the
radius.
31. Nonmetal ions gain electrons in their valence shell, increasing e- to e- repulsion causing orbitals to increase in
size.
32. Zeff is greater. The force of attraction between the nucleus and the valence e- is stronger.
33. Full outer energy level, sometimes called an octet.
34.
a. Xe, I, Ba, Cs
b. Kr, Br, Se, Sr
c. Li, K, Cs, F
35.
a. S, Al, Mg, Na
b. F, Br, I, At
c. Se, Ga, Zn, Cu
36. This is the charge that the valence electrons experience as a result of shielding electron interference.
𝑍𝑒𝑓𝑓 = 𝑍 − 𝑐𝑜𝑟𝑒 𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑛𝑠
37. Ca: 20-18=+2, Br: 17-10=+7
The greater the Zeff the greater the force of attraction from the nucleus on the
outer energy shell, thus pulling it in closer.
38. Energy required to remove an electron from an atom. Coulomb’s Law describes the relationship. 𝐸 ≈
39.
40.
41.
42.
43.
44.
45.
𝑄1 𝑄2
𝑑
IE is
inversely related to distance from nucleus and directly related to charge.
The 3rd electron being removed is a core electron, closer to the nucleus, therefore according to Coulombs law
requires more energy.
Al first IE is for an electron found in the p-sublevel, it’s lower energy than the s-sublevel on the same energy level,
therefore; easier to remove.
(A)
Al. The big jump in IE occurs after the removal of the 3rd e-. The next e- comes from the second energy level.
(D)
You can conclude that there are the same number of electrons found at that energy.