Chem 121
Sp 2014
CHEM 121
Chapter 8
Bonding: General Concepts
KEY
1. How many unpaired electrons are in the Lewis electron-dot symbol for an oxygen atom?
2
2. Which of the following shows the incorrect number of valence electrons in parentheses?
Ca (2)
3. Which of the following exhibits metallic bonding?
PCl3
MgCl2
O3
P
6. What is main energy level from which electrons are lost when tungsten forms a cation?
5
S
4
Se (4)
Au-Pd alloy
+
4. Which of the following ions does not have a noble-gas configuration?
0
2-
Y
1
As (5)
Li (1)
Cl (7)
NH3
3-
Sc
3+
Mg
2+
5. Which of the following is most likely possible for an alkaline earth metal?
3
2
1
6
4
7. Which of the following processes would be expected to be exothermic?
+
K (g) + Br (g) → KBr(s)
Br2 (g) → 2 Br(g)
K(s) → K(g)
+
K(g) → K (g) + e
Br2 (l) → Br2 (g)
8. In which of the following sets are all of the ions or atoms isoelectronic with each other?
+
+
(i) K , Na , Mg
2+
+
(ii) Ag , Cd
A) v
2+
2-
2-
2+
(iii) Se , Te , Kr
B) i
(iv) Ru , Rh
C) ii, iv, and v
D) iii
3+
3-
2-
(v) As , Se , Br
E) iv
-
F) ii
9. In which of the following sets are all of the ions or atoms isoelectronic with one another?
+
(i) Ba, Lu , Hf
3+
4+
2+
(ii) Nb , Y , Rb
A) ii only
+1
2-
-
B) iii and iv only
10. Which of the following has the greatest diameter?
Na
-
S-S
(iv) Br , Kr, Rb
C) i only
11. The anion ICl4 has how many total valence electrons?
12. Which of the following bonds is polar?
-
(iii) Te , I , Xe
+
Na
28
F-F
D) iv only
-
34
Cl
E) i and ii only
35
8
36
O-S
-
S
3-
14. Which one of the following ions has a noble-gas electron configuration?
I
Fe
+
3+
K
Se
2-
-
O
Cu
2+
Cr
2+
3+
15. Which ionic compound is not expected to form from a combination of the following pairs of elements?
SrO
Ca3N2
Zn
17. Based upon electron configuration, which ion would magnesium most likely form?
2-
2
[Ar]3s 3p
6
Mg
2+
Mg
2
[Ne]3s 3p
2
2+
GaS
16. Which ionic compound is not expected to form from a combination of the following pairs of elements?
K 3N
RbCl
CsO
18. Which of the following is the electron configuration for the S ion?
F) iii only
Na
O-O
13. Which ion below has a noble-gas electron configuration?
+
2-
Li2S
AlN
Mg
-
B 2O 3
Mg
2
[Ne]3s 3p
MgS
6
6+
Mg
2
[Ar]4s 3d 4p
19. Which of the following is correctly arranged with respect to the size of the atom/ion?
+
(i) Br > Br > Br
-
+
+
(ii) Rb > K > Na
A) i
+
2+
(iii) Ru > Ru > Ru
B) i and ii
C) ii
D) iii
3+
E) ii and iii
F) i and iii
2-
20. For the following set of atoms and ions, arrange the members in order of decreasing size:
2-
2-
-
Te > Se > Br > Br > Rb
2-
+
2-
2-
2-
-
+
2-
2-
Te > Se > Br > Br > Rb
-
Se > Te > Br > Br > Rb
+
2-
-
-
+
-
Te , Br, Rb , Br , Se
2-
Te > Br > Se > Br > Rb
Te > Se > Br > Rb > Br
+
+
10
6-
2-
2
Chem 121
Sp 2014
21. Which of the following sets of atoms and ions has the members arranged in order of increasing size?
Al
3+
< Si
4+
3-
<P <S
2-
3-
2-
P < S < Al
3+
< Si
4+
Si
4+
< Al
3+
3-
<P <S
22. Which ion in the isoelectronic series below has the largest radius?
N
2-
3-
Si
F
-
4+
< Al
Na
3+
+
2-
<S <P
O
2-
Al
23. By referring only to the periodic table, arrange the following in order of increasing electronegativity:
Ga < As < S < P < O < F
As < Ga < P < S < O < F
Ga < P < As < S < O < F
Ga < As < P < O < S < F
Ga < As < P < S < O < F
Ga < As < P < S < F < O
3-
2-
3-
4+
S < P < Si < Al
3+
Ga, P, As, S, O, F
24. By referring only to the periodic table, arrange the following atoms in order of increasing electronegativity. Al, Si, S, P, In, Ga
S < P < Si < Al < Ga < In
In < Ga < Al < S < P < Si
Al < Si < P < S < Ga < In
In < Ga < Al < Si < P < S
Al < Ga < In < Si < P < S
25. Which of the atoms below is the most electronegative?
F
26. Which order is correct for increasing polarity (least polar first)?
A<B<C<D
D<B<C<A
Ca
Rb
Si
Si-Cl
A
S-Cl
B
P-Cl
C
C<B<D<A
Cl
C<D<B<A
27. Which combination of atoms would most likely produce a covalent bond?
Si-Si
D
D<C<B<A
Cd, Cl
28. How many valence electrons are involved in writing the Lewis structure of AsF3?
Fe, S
5
8
Cu, Se
21
32
K, O
N, F
26
29. In which of the following are there two bonding pairs and two nonbonding pairs on an atom? PH3 BF3 CH4 OF2 BeCl2 NCl3
+
-
-
30. Predict the order of the N-O bond lengths in NO , NO2 , and NO3 .
+
-
NO shortest, NO2 longest
+
-
+
NO shortest, NO3 longest
-
-
NO longest, NO2 shortest
-
NO3 shortest, NO2 longest
31. Consider the molecule H2N-CH2-CH2-CO2H. Examine the Lewis structure for this molecule and determine which of the following
statements is incorrect.
There are eleven single bonds in this molecule.
There are three single bonds and one lone pair of electrons around the N atom.
There is one double bond in this molecule.
There are five lone pairs of electrons in this molecule.
There is one oxygen-oxygen bond in this molecule.
32. What is the number of bonding and nonbonding electron pairs around the central atom in each of the following? NH3, H2S, CO2
NH3: (3 bonding, 1 nonbonding); H2S: (2 bonding, 1 nonbonding); CO2: (4 bonding, 0 nonbonding)
NH3: (3 bonding, 1 nonbonding); H2S: (2 bonding, 2 nonbonding); CO2: (2 bonding, 0 nonbonding)
NH3: (3 bonding, 0 nonbonding); H2S: (2 bonding, 1 nonbonding); CO2: (4 bonding, 0 nonbonding)
NH3: (3 bonding, 0 nonbonding); H2S: (2 bonding, 2 nonbonding); CO2: (4 bonding, 0 nonbonding)
NH3: (3 bonding, 1 nonbonding); H2S: (2 bonding, 2 nonbonding); CO2: (4 bonding, 0 nonbonding)
33. Which of the following molecules has two resonance structures?
CO2
CH4
ClO4
34. Use bond enthalpies to estimate the enthalpy change for the following gas-phase reaction:
-
H2CCH2 < HCCH < H3CCH3
HCCH,
H3CCH3 < H2CCH2 < HCCH
37. Which of the following orders of electronegativity is incorrect?
H2CCH2,
4
NO3
-
2
6
3
5
H3CCH3
HCCH < H3CCH3 < H2CCH2
I < Br < Cl
-
CH4 + Cl2 → CH2Cl2 + H2
-45 kJ/mol
35. How many pairs of electrons are there around the central atom in the Lewis structure of SeF4?
36. Arrange the following in order of increasing C-C bond lengths:
CH3CO2
C<N<O
C < Si < P
HCCH < H2CCH2 < H3CCH3
Se < S < O
Si < P < N
3+
Chem 121
Sp 2014
-
38. How many valence electrons are shown in the Lewis structure of CN ?
9
12
8
13
10
39. The C-O bond lengths in H2CO are shorter than would be expected for C-O single bonds. Rationalize this observation.
A triple bond is formed.
A double bond is formed.
The two hydrogens form bonds with each other.
Oxygen is more electronegative than carbon.
Carbon uses its d electrons to form stronger bonds.
40. Write Lewis structures for the following:
(i) HOBr
(ii) H2O2 (the O atoms are bonded to one another)
(iii) H2CO (both H atoms are bonded to C)
Pick the incorrect response below.
There is a double bond in structure iii.
Oxygen in structure i has two nonbonded pairs of electrons.
The total number of bonds in structure ii is three.
There are double bonds between the oxygens in structure ii.
There are three nonbonding pairs of electrons around bromine in structure i.
-
-
41. What is the formal charge on the chlorine atom in the chlorite ion ClO2 and the chlorate ion ClO3 ?
0, 1+
1+ in both
3+, 5+
0 in both
1+, 2+
2+ in both
42. Is the C-O bond in CH3OH longer or shorter than the C-O bond in CH3COCH3? Why?
longer; CH3COCH3 is a bigger molecule.
shorter; CH3COCH3 has a triple bond.
longer; CH3COCH3 has a double bond.
They are the same length.
shorter; CH3COCH3 has a double bond.
-
43. Write a single, stable Lewis structure for ClO2 . What are the formal charges on the atoms?
Cl 0; O 0
Cl 1-; O 0
Cl 1+; O 1-
Cl 0; O 0; O 1-
Cl 1-; O 1+
2-
2-
44. Using Lewis structures that satisfy the octet rule, determine the # of electrons around the central S atom in SO3 and SO4 .
10, 10
8, 12
8, 8
10, 12
6, 12
6, 8
45. Which is the best Lewis structure for COS? (Formal charges are not shown.)
C
S
O
S
C
O
S
C
O
S
C
O
C
O
S
46. The Lewis structures of which of the following compounds obey the octet rule?
(i) SO3
2-
(ii) BH3
(iii) I3
A) iv
-
(iv) AsF6
-
B) i and v
(v) O2
-
C) v
D) iii
E) ii
F) i
-
47. How many pairs of electrons are there around the central atom in the Lewis structure of ICl2 ?
48. Which of the following does not exhibit bond resonance?
NO2
-
O3
SO4
2-
CO3
2-
3
H 2O 2
5
4
2