Suggested problems Chapter 9
9.23
Examine each of the following electron-dot formulas and decide whether the formula is correct, or whether you
could write a formula that better approximates the electron structure of the molecule. State which concepts or
rules you use in each case to arrive at your conclusion.
a.
9.27
N N
b.
HC F
O
c.
Cl C N
O
d. H O C O H
Sodium, Na, reacts with element X to form an ionic compound with the formula Na3X.
a. What is the formula of the compound you expect to form when calcium, Ca. reacts with element X?
b. Would you expect this compound to be ionic or molecular?
9.29
Write Lewis symbols for the following:
a. P
9.31
b. P3-
d. Ga3+
Use Lewis symbols to represent the transfer of electrons between the following atoms to give ions with noblegas configurations:
a. Ca and Br
9.33
c. Ga
b. K and I
For each of the following, write the electron configuration and Lewis symbol:
a. As
b. As3+
c. Se
d. Se2-
9.35
Write the electron configurations of Bi and Bi3+.
9.37
Give the electron configurations of Ni2+ and Ni3+.
9.39
Arrange the members of each of the following pairs in order of increasing radius and explain the order:
a. Sr, Sr2+
b. Br, Br-
9.41
Without looking at Table 9.3, arrange the following by increasing ionic radius: Se 2-, Te2-, S2-. Explain how you
arrived at this order. (You may use a periodic table).
9.43
Arrange the following in order of increasing ionic radius: F-, Na+, and N3-. Explain this order. (You may use a
periodic table).
9.45
Use Lewis symbols to show the reaction of atoms to form hydrogen selenide, H2Se. Indicate bonding pairs and
lone pairs in the electron-dot formula of this compound.
9.47
Assuming that the atoms form the normal number of covalent bonds, give the molecular formula of the simplest
compound of arsenic and bromine atoms.
9.49
Using the periodic table, arrange the following in order of increasing electronegativity:
a. P, O, N
b. Na, Al, Mg
c. C, Al, Si
9.51
Arrange the following bonds in order of increasing polarity using electronegativities of atoms: P-O, C-Cl, As-Br.
9.53
Indicate the partial charges for the bonds given in Problem 9.51, using the symbols + and -.
9.55
Write Lewis formulas for the following molecules:
a. Br2
9.57
c. HNO2
b. SnCl3-
c. S22-
Write resonance descriptions for the following:
a. HNO3
9.63
b. COBr2
Write Lewis formulas for the following ions:
a. ClO-
9.61
c. NF3
Write Lewis formulas for the following molecules:
a. P2
9.59
b. H2S
b. SO3
Use resonance to describe the electron structure of nitromethane, CH3NO2. The skeleton structure is
H
H
O
C
N
O
H
9.65
Write Lewis formulas for the following:
a. XeF2
9.67
c. BeBr2
b. CO
c. HNO3
For each of the following, use formal charges to choose the Lewis formula that gives the best description of the
electron distribution:
a. SOF2
9.77
b. TlCl2+
Write a Lewis formula for each of the following assuming that the octet rule holds for the atoms. Then obtain
the formal charges of the atoms.
a. O3
9.71
d. XeF5+
c. TeF6
Write Lewis formulas for the following:
a. BCl3
9.69
b. SeF4
b. H2SO3
c. HClO2
One of the following compounds has a carbon-nitrogen bond length of 116 pm; the other has a carbon-nitrogen
bond length of 147 pm. Match a bond length with each compound.
H
H
H
C
N
H
H
H
methylamine
H
C
C
H
acetonitrile
N
9.81
For each of the following pairs of elements, state whether the binary compound formed is likely to be ionic or
covalent. Give the formula and name of the compound.
a. Sr, O
b. C, Br
c. Ga, Cl
d. N, Br
9.85
Iodic acid, HIO3, is a colorless, crystalline compound. What is the electron-dot formula of iodic acid?
9.97
The compound S2N2 has a cyclic structure with alternating sulfur nitrogen atoms. Draw all resonance formulas in
which the atoms obey the octet rule. Of these, select those in which the formal charges are closest to zero.
9.99
The atoms in N2O5 are connected as follows:
O
O
N
O
O
N
O
No attempt has been made here to indicate whether a bond is single or double or whether there is resonance.
Obtain the Lewis formula (or formulas). The N-O bond lengths are 118 pm and 136 pm. Indicate the lengths of
the bonds in the compound.