Basics ‹ 65
- C—Most of the other elements are metals.
Metals usually form monatomic cations. Neon,
Ne, a noble gas, normally does not form ions. - A—The element cannot be another metal (Na).
The polyatomic ion must be XO 32 -. Of the
choices, only carbon gives a polyatomic ion with
this general formula. The carbonate ion has the
formula CO 32 -. - A—Based on their positions on the periodic
table:
C +4 to –4
F –1 and 0 (element)
O –2 to 0
Ca +2 and 0- D—Isotopes MUST have the same number of
protons. Different isotopes of an element have
different numbers of neutrons. - A—All the others are listed in order of decreas-
ing radius. Ions in the same column and with
the same charge increase in size when going
down a column the same as atoms. Atoms in
the same row increase in size toward the left
side. This argument is not sufficient for the free-
response portion of the exam. - B—In general, the element farthest from F
on the periodic table will have the lowest elec-
tronegativity. There are exceptions, but you
normally do not need to concern yourself with
exceptions. - D—The very large iodine atom (near the bottom
of the periodic table) gains an electron to make
it even larger. This reasoning is not sufficient for
the free-response portion of the exam. - D—The definition of electron affinity is the
energy change when a ground-state gaseous
atom adds an electron. - D—The more electrons removed, the higher the
values should be. The large increase between the
first and second ionization energies indicates a
change in electron shell. The element X has only
1 valence electron. This is true for Na. For the
other elements, the numbers of valence electrons
are as follows: Mg, 2; Cl, 7; and Al, 3.
10. A—An increase in the number of protons in the
nucleus has a greater attraction (greater effective
nuclear charge) for the electrons being added
in the same energy level. Thus, the electrons
are pulled closer to the nucleus, and the size
slightly decreases. This thought process should
be used on the free-response portion of the AP
exam; however, simply remembering that radii
decrease across a period is sufficient for most
multiple- choice questions.
11. A—The only other gas is radon, and it is inert.
12. B—Sodium is a metal on the left side of the
periodic table. Metals on the left side of the peri-
odic table are very reactive. Radon is not a metal.
13. B—Ferrate(III) means Fe^3 +, while trisoxalato
means (C 2 O 4 ) 36 - ; three potassium atoms are
needed to balance the charge.
14. A—B is blue; C is orange; and D is pink to red.
15. C—This is the only choice containing both a
metal and a nonmetal. Compounds contain-
ing a metal and a nonmetal are usually ionic.
Compounds containing a nonmetal or metalloid
and a nonmetal are usually molecular (covalent).
16. B—Prefixes are commonly used when naming
molecular compounds. Some examples are
carbon dioxide, CO 2 , and dibromine trioxide,
Br 2 O 3.
17. C—Aluminum forms a protective oxide coating.
18. B—Gallium, adjacent to Ge on the periodic
table, is one of the elements that will improve
the conductivity of germanium.
19. A—B is purple; C is green; and D is colorless.
20. A—Fractional crystallization works because the
less soluble material separates first.
21. D—The acids are hypobromous acid, HBrO;
bromous acid, HBrO 2 ; bromic acid, HBrO 3 ;
perbromic acid, HBrO 4.
22. C—Adding a weak base solution, such as
NaHCO 3 , which will not only neutralize the
acid but help disperse the heat, is the best choice.
23. B—A solution containing a colored substance is
necessary. A KMnO 4 solution is intense purple.
❯ Answers and Explanations