The Foundations of Chemistry

302 CHAPTER 7: Chemical Bonding

*45.Write Lewis structures for the following molecules:

(a) Formic acid, HCOOH, in which the atomic arrange-

ment is

O

HCOH

(b) Acetonitrile, CH 3 CN;

(c) Vinyl chloride, CH 2 CHCl, the molecule from which

PVC plastics are made.

*46.Write Lewis structures for the following molecules:

(a) Tetrafluoroethylene, C 2 F 4 , the molecule from which

Teflon is made;

(b) Acrylonitrile, CH 2 CHCN, the molecule from which

Orlon is made.

*47.What do we mean by the term “resonance”? Do the res-

onance structures that we draw actually represent the

bonding in the substance? Explain your answer.

*48.Careful examination of the ozone molecule indicates that

the two outer oxygens are the same distance from the cen-

tral oxygen. Write Lewis formulas or resonance structures

that are consistent with this finding.

*49.Draw resonance structures for the nitric acid molecule.

*50.We can write two resonance structures for toluene,

C 6 H 5 CH 3 :

How would you expect the carbon–carbon bond lengths

in the six-membered ring to compare with the

carbon–carbon bond length between the CH 3 group and

the carbon atom on the ring?

*51.Write resonance structures for the formate ion,

HCOO.

*52.Write resonance structures for the nitrate ion, NO 3 .

*53.Write Lewis formulas for (a) H 2 NOH (i.e., one H

bonded to O); (b) S 8 (a ring of eight atoms); (c) PCl 3 ;

(d) F 2 O 2 (O atoms in center, F atoms on outside); (e) CO;

(f) SeCl 6.

*54.Write the Lewis formula for each of the following covalent

compounds. Which ones contain at least one atom with a

share in less than an octet of valence electrons? (a) BeBr 2 ;

(b) BBr 3 ; (c) NCl 3 ; (d) AlCl 3.

*55.Which of the following species contain at least one atom

that violates the octet rule?

(a) F Cl (b) O Cl O (c) F Xe F

H

H

H H

H

H

H

H

C

C

C

C C

C C

H

H

H H

H

H

H

H

C

C

C

C C

C C

(d)

*56.Write the Lewis formula for each of the following mole-

cules or ions. Which ones contain at least one atom with

a share in less than an octet of valence electrons? (a)

CH 2 Cl 2 ; (b) BF 3 ; (c) BCl 4 ; (d) AlF 4 .

*57.None of the following is known to exist. What is wrong

with each one?

(a) (d)

(b)

(c)

*58.Write the Lewis formula for each of the following mole-

cules or ions. Which ones contain at least one atom with

a share in more than an octet of valence electrons? (a) PF 6 ;

(b) AsCl 5 ; (c) ICl 3 ; (d) C 2 H 6.

*59.Suppose that “El” is the general symbol for a representa-

tive element. In each case, in which periodic group is El

located? Justify your answers and cite a specific example

for each one.

(a) (c)

(b) (d)

*60.Suppose that “El” is the general symbol for a representa-

tive element. In each case, in which periodic group is El

located? Justify your answers and cite a specific example

for each one.

(a) (c)

(b) (d)

*61.Many common stains, such as those of chocolate and other

fatty foods, can be removed by dry-cleaning solvents such

as tetrachloroethylene, C 2 Cl 4. Is C 2 Cl 4 ionic or covalent?

Write its Lewis formula.

H

H El H



O El O

H

H

H El H



Br

Br

Br El

HHO El

O H

O El O

2 

O

H O El O

O

O El O



OON 

H H OPCl

Cl

Na O

Na

Cl OS

O

O

O O

O

S

2 

(e) O

• O Cl