Bonding ❮ 163cannot exceed an octet. Only answer B is limited
to elements that can exceed an octet.- C—The ionic bonds are present in the calcium
compounds (eliminating all but A and C). The
phosphide ion has no internal bonding (elimi-
nating A); however, the carbonate ion has both
s and p bonds. - A—This hybridization requires a geometrical
shape with three corners. - B—One or more Lewis structures may help you.
A is an irregular tetrahedron (seesaw); C and D
are square planar. - C—Draw the Lewis structures. The number of
unshared pairs are as follows: (A) 1; (B) 0; (C) 3;
(D) 1. - B—All molecules are polar except B.
- A—Drawing one or more Lewis structures may
help you. Only A and C are polar. Only the
ammonia has hydrogen bonding, which is very,
very polar. - B—Calcium is a metal; therefore, the process
shown is breaking metallic bonds. All the species
in A and D are covalently bonded molecules.
Potassium chloride, KCl, is an ionic compound,
and separating the ions involves breaking ionic
bonds.
17. A—Increasing covalent character means decreas-
ing electronegativity difference. Chlorine is a
constant, so the electronegativity differences of
concern are all relative to chlorine. The most
covalent would be a bond with an electronegativ-
ity difference of 0, which occurs when chlorine
is bonded to chlorine (Cl–Cl). In general, the
covalent character will decrease (ionic character
will increase) when moving from chlorine to
the left on the periodic table. The Na–Cl bond
would be the most ionic (least covalent). Only
answer A has the bonds in the correct order.
18. B—The SF 6 molecule has six s bonds and no p
bonds. The other three molecules have double
or triple bonds. All double bonds are a combina-
tion of an s bond and a p bond, and all triple
bonds are a combination of one s bond and two
p bonds.
19. B—The process of resonance tends to equalize
the lengths of the bonds involved.
20. C—The ion NO 2 + is a linear species (bond angle
180 °) because there are no lone electron pairs
on the nitrogen atom, and the other two are
bent species (bond angle < 180 °) due to the lone
electron (≈ 134 °) or pair of electrons (≈ 118 °) on
the nitrogen. The presence of resonance does
not alter the result.
❯ Free-Response Question
You have 15 minutes to answer the following question. You may use a calculator and the
tables in the back of the book.Question
Answer the following questions about structure and bonding.
(a) Which of the following tetrafluoride compounds is nonpolar? Use Lewis electron-dot
structures to explain your conclusions.
SiF 4 SF 4 XeF 4
(b) Rank the following compounds in order of increasing melting point. Explain your
answer. Lewis electron-dot structures may aid you.
SnF 2 SeF 2 KrF 2
(c) Use Lewis electron-dot structures to show why the carbon–oxygen bonds in the oxalate
ion (C 2 O 4 2–) are all equal.
(d) When PCl 5 is dissolved in a polar solvent, the solution conducts electricity. Explain
why. Use an appropriate chemical equation to illustrate your answer.