Exercises 347How many regions of high electron density are there about
each of the three carbon atoms?
29.Pick the member of each pair that you would expect to
have the smaller bond angles, if different, and explain why.
(a) SF 2 and SO 2 ; (b) BF 3 and BCl 3 ; (c) SiF 4 and SF 4 ;
(d) NF 3 and OF 2.
30.Draw a Lewis formula, sketch the three-dimensional shape,
and name the electronic and ionic geometries for the fol-
lowing polyatomic ions. (a) H 3 O; (b) PCl 6 ; (c) PCl 4 ;
(d) SbCl 4 .
31.As the name implies, the interhalogens are compounds that
contain two halogens. Write Lewis formulas and three-
dimensional structures for the following. Name the
electronic and molecular geometries of each. (a) BrF 3 ;
(b) BrF; (c) BrF 5.
32.A number of ions derived from the interhalogens are
known. Write Lewis formulas and three-dimensional
structures for the following ions. Name the electronic and
molecular geometries of each. (a) IF 4 ; (b) ICl 4 ;
(c) BrF 4 ; (d) ClF 32 .
33.(a) Write a Lewis formula for each of the following mol-
ecules: BF 3 ; NF 3 ; ClF 3. (b) Contrast the molecular
geometries of these three molecules. Account for differ-
ences in terms of the VSEPR theory.
34.(a) Write a Lewis formula for each of the following mol-
ecules: SiF 4 ; SF 4 ; XeF 4. (b) Contrast the molecular
geometries of these three molecules. Account for differ-
ences in terms of the VSEPR theory.
35.Write the Lewis formulas and predict the shapes of these
very reactive carbon-containing species: H 3 C(a carboca-
tion); H 3 CS(a carbanion); and SCH 2 (a carbene whose
unshared electrons are paired).
36.Write the Lewis formulas and predict the shapes of (a) I 3 ;
(b) TeCl 4 ; (c) XeO 3 ; (d) NOBr (N is the central atom);
(e) NO 2 Cl (N is the central atom); (f) SOCl 2 (S is the cen-
tral atom).
37.Describe the shapes of these polyatomic ions: (a) BO 33 ;
(b) AsO 43 ; (c) SO 32 ; (d) NO 3 .
38.Would you predict a nitrogen–oxygen bond to have the
same magnitude of bond polarity as a hydrogen–oxygen
bond? Explain your answer.
39.Which of the following molecules are polar? Why?
(a) CH 4 ; (b) CH 3 Br; (c) CH 2 Br 2 ; (d) CHBr 3 ; (e) CBr 4.
40.Which of the following molecules are polar? Why?
(a) CdI 2 ; (b) BCl 3 ; (c) AsCl 3 ; (d) H 2 O; (e) SF 6.
41.Which of the following molecules are nonpolar? Justify
your answer. (a) SO 3 ; (b) IF; (c) Cl 2 O; (d) NF 3 ; (e) CHCl 3.
42.The PF 2 Cl 3 molecule is nonpolar. Use this information to
sketch its three-dimensional shape. Justify your choice.
*43.In what two major ways does the presence of unshared pairs
of valence electrons affect the polarity of a molecule?
Describe two molecules for which the presence of unshared
pairs on the central atom helps to make the molecules
polar. Can you think of a bonding arrangement that has
unshared pairs of valence electrons on the central atom but
that is nonpolar?
*44.Is the phosphorus–chlorine bond in phosphorus trichlo-
ride a polar bond? Is phosphorus trichloride a polar
molecule? Explain.
*45.Is the phosphorus–chlorine bond in phosphorus pen-
tachloride a polar bond? Is phosphorus pentachloride a
polar molecule? Explain.
*46.Write the Lewis formula for each of the following. Indi-
cate which bonds are polar. (See Table 6-3.) Indicate which
molecules are polar. (a) CS 2 ; (b) AlF 3 ; (c) H 2 S; (d) SnF 2.
*47.Write the Lewis formula for each of the following. Indi-
cate which bonds are polar. (See Table 6-3.) Indicate which
molecules are polar. (a) OF 2 ; (b) CH 4 ; (c) H 2 SO 4 ; (d)SnF 4.Valence Bond Theory
*48.Describe the orbital overlap model of covalent bonding.
*49.Briefly summarize the reasoning by which we might have
predicted that the formula of the simplest stable hydro-
carbon would be CH 2 , if we did not consider hybridization.
Would this species satisfy the octet rule?
*50.What is the hybridization of the central atom in each of
the following? (a) NCl 3 ; (b) molecular AlCl 3 ; (c) CF 4 ;
(d) SF 6 ; (e) IO 4 .
*51.What is the hybridization of the central atom in each of
the following? (a) IF 4 ; (b) SiO 44 ; (c) AlH 4 ; (d) NH 4 ;
(e) PCl 3 ; (f) ClO 3 .
*52.(a) Describe the hybridization of the central atom in each
of these covalent species. (1) CHCl 3 ; (2) CH 2 Cl 2 ; (3) NF 3 ;
(4) PO 43 ; (5) IF 6 ; (6) SiF 62 . (b) Give the shape of each
species.
*53.Describe the hybridization of the underlined atoms in
C 2 F 6 , C 2 F 2 , N 2 F 4 , and (H 2 N) 2 CO.
*54.Prepare a sketch of the molecule CH 3 CHUCH 2 showing
orbital overlaps. Identify the type of hybridization of
atomic orbitals on each carbon atom.
*55.After comparing experimental and calculated dipole
moments, Charles A. Coulson suggested that the Cl atom
in HCl is sphybridized. (a) Give the orbital electronic
structure for an sphybridized Cl atom. (b) Which HCl
molecule would have a larger dipole moment—one in
which the chlorine uses pure porbitals for bonding with
the H atom or one in which sphybrid orbitals are used?
*56.Predict the hybridization at each carbon atom in each of
the following molecules.
(a) acetone (a common solvent)HH
HCHO H
CCC H