The Foundations of Chemistry

Exercises 349

*58.How many sigma and how many pi bonds are there in each
of the following molecules?

*59.How many sigma and how many pi bonds are there in each
of the following molecules?

C

Cl

C

N C

H

H

(c)

H

H C

H

(a) C

H

H

O H

C C

(d) CHCCC H

H H

C C

Cl

C

H Cl

H

(b) C

H

C H

H

HC

H

H

C

(c)

O

O

H

C

HH

HCC H

H H H

(a) C

*65.Write the Lewis formulas and predict the hybrid orbitals

and the shapes of these polyatomic ions and covalent mol-

ecules: (a) HgCl 2 ; (b) BF 3 ; (c) BF 4 
; (d) SbCl 5 ; (e) SbF 6 
.

*66.(a) What is the hybridization of each C in these molecules?

(i) H 2 CUO; (ii) HCqN; (iii) CH 3 CH 2 CH 3 ; (iv) ketene,

H 2 CUCUO. (b) Describe the shape of each molecule.

*67.The following fluorides of xenon have been well charac-

terized: XeF 2 , XeF 4 , and XeF 6. (a) Write Lewis formulas

for these substances and decide what type of hybridization

of the Xe atomic orbitals has taken place. (b) Draw all of

the possible atomic arrangements of XeF 2 , and discuss your

choice of molecular geometry. (c) What shape do you pre-

dict for XeF 4?

*68.Iodine and fluorine form a series of interhalogen molecules

and ions. Among these are IF (minute quantities observed

spectroscopically), IF 3 , IF 4 
, IF 5 , IF 6 
, and IF 7. (a) Write

Lewis formulas for each of these species. (b) Identify the

type of hybridization that the orbitals of the iodine atom

have undergone in each substance. (c) Identify the shape

of the molecule or ion.

Mixed Exercises

*69.In the pyrophosphate ion, P 2 O 74 
, one oxygen atom is

bonded to both phosphorus atoms.

60.Describe the bonding in the carbide ion, C 22
, with a
three-dimensional VB structure. Show the orbital overlap,
and label the orbitals.
61.Write Lewis formulas for molecular oxygen and ozone.
Assuming that all of the valence electrons in the oxygen
atoms are in hybrid orbitals, what would be the hybridiza-
tion of the oxygen atoms in each substance? Prepare
sketches of the molecules.
62.Draw a Lewis formula and a three-dimensional structure
for each of the following polycentered molecules. Indi-
cate hybridizations and bond angles at each carbon
atom. (a) butane, C 4 H 10 ; (b) propene, H 2 CUCHCH 3 ;
(c) 1-butyne, HCmCCH 2 CH 3 ; (d) acetaldehyde,
CH 3 CHO.
63.How many bonds and how many bonds are there in
each of the molecules of Exercise 62?
*64.(a) Describe the hybridization of N in each of these
species.

(i) (ii) (iii) (iv)

(v)

(b) Give an orbital description for each species, specify-

ing the location of any unshared pairs and the orbitals used

for the multiple bonds.

H 2 NNH 2.

NH 3 ; NH 4 ; HN NH; HC N ;

(d) CH 2 CHCH 2 OCH 2 CH 3

H

C

H

O

HCH

H H

C

(b)

Write a Lewis formula, and sketch the three-dimensional

shape of the ion. Describe the electronic and molecular

geometries with respect to the central O atom and with

respect to each P atom.

*70.Briefly discuss the bond angles in the hydroxylamine mol-

ecule in terms of the ideal geometry and the small changes

caused by electron-pair repulsions.

*71.Repeat Exercise 70 for the nitrite ion.

*72.The methyl free radical TCH 3 has bond angles of about

120°, whereas the methyl carbanion SCH 3 
has bond

O N

O

ON

O

H O H

H

N