The Foundations of Chemistry

Exercises 351

BUILDING YOUR KNOWLEDGE

*85.Sketch three-dimensional representations of the follow-

ing molecules and indicate the direction of any net dipole

for each molecule: (a) CH 4 ; (b) CH 3 Cl; (c) CH 2 Cl 2 ;

(d) CHCl 3 ; (e) CCl 4.

*86.Write the Lewis formula and identify the electronic geom-

etry and molecular geometry for each polyatomic species

in the following equations:

(a) HH 2 O nH 3 O

(b) NH 3 HnNH 4 

*87.Draw the Lewis formula of an ammonium ion. Describe

the formation of the ammonium ion from ammonia plus

H. Does the hybridization of orbitals on nitrogen change

during the formation of the ammonium ion? Do the bond

angles change?

*88.The following is an incomplete Lewis formula for a mol-

ecule. This formula has all the atoms at the correct places,

but it is missing several valence electrons. Complete this

Lewis formula, including lone pairs.

*89.The following is an incomplete Lewis formula for a mol-

ecule. This formula has all the atoms at the correct places,

but it is missing several valence electrons. Complete this

Lewis formula, including lone pairs.

O

O

H

C

H

H

HHBr H

C CC N

Cl

C

H Br

HCC O