Chemical Bonding
Review
Copyright © Cengage Learning. All rights reserved.
12 | 1
QUESTION
Most chemical bonds consist of electrostatic attractive forces and
are called ____ bonds, or of shared electrons and are called
_____bonds.
1.
2.
3.
4.
electric; shared
ionic; covalent
ionic; molecular
electronic; coordinate
Copyright © Cengage Learning. All rights reserved.
12 | 2
ANSWER
Choice #2 properly identifies the bonds as ionic and covalent.
Copyright © Cengage Learning. All rights reserved.
12 | 3
QUESTION
When electrons in a covalent bond are shared equally the bond is
_________, but if the electrons are not shared equally the
bond is ________, which means that it has a positive side and
a negative side.
1.
2.
3.
4.
ionic; covalent
strong; weak
nonpolar; polar
stable; unstable
Copyright © Cengage Learning. All rights reserved.
12 | 4
ANSWER
Choice #3 is the correct answer.
Copyright © Cengage Learning. All rights reserved.
12 | 5
QUESTION
When considering a bond between two atoms, the greater the
difference in ____________, the more __________is the bond.
1.
2.
3.
4.
polarity; divided
atomic weight; nonpolar
electronegativity; polar
electronegativity; nonpolar
Copyright © Cengage Learning. All rights reserved.
12 | 6
ANSWER
Choice #3 correctly expresses the idea that bonds become more
polar as the difference in the electronegativity of the atoms
increases.
Copyright © Cengage Learning. All rights reserved.
12 | 7
QUESTION
Rank the following bonds from least polar to most polar:
Si-Cl P-Cl Mg-Cl S-Cl
1.
2.
3.
4.
P-Cl, S-Cl, Si-Cl, Mg-Cl
Mg-Cl, Si-Cl, P-Cl, S-Cl
Mg-Cl, S-Cl, P-Cl, Si-Cl
S-Cl, P-Cl, Si-Cl, Mg-Cl
Copyright © Cengage Learning. All rights reserved.
12 | 8
ANSWER
Choice #3 is the correct answer. Bonds become more polar as the
difference in the electronegativity of the atoms increases.
Copyright © Cengage Learning. All rights reserved.
12 | 9
QUESTION
Choose the bond that is the most polar.
1.
2.
3.
4.
Sr–O
C–O
N–N
Fe–P
Copyright © Cengage Learning. All rights reserved.
12 | 10
ANSWER
Choice #1 is the correct answer. Bonds become more polar as the
difference in the electronegativity of the atoms increases.
Copyright © Cengage Learning. All rights reserved.
12 | 11
QUESTION
Which of the following bonds would be the least polar yet still be
considered polar covalent?
1.
2.
3.
4.
Mg–O
N–O
Si–O
O–O
Copyright © Cengage Learning. All rights reserved.
12 | 12
ANSWER
Choice #2 is the correct answer. To be considered polar covalent,
unequal sharing of electrons must still occur. Choose the bond
with the least difference in electronegativity yet there is still some
unequal sharing of electrons.
Copyright © Cengage Learning. All rights reserved.
12 | 13
QUESTION
Which of the following bonds would be the most polar without
being considered ionic?
1.
2.
3.
4.
Mg–O
N–O
Si–O
O–O
Copyright © Cengage Learning. All rights reserved.
12 | 14
ANSWER
Choice #3 is the correct answer. To not be considered ionic,
generally the bond needs to be between two nonmetals. The most
polar bond between the nonmetals occurs with the bond that has
the greatest difference in electronegativity.
Copyright © Cengage Learning. All rights reserved.
12 | 15
QUESTION
The difference in electronegativity between hydrogen and iodine
is (4.0 – 2.5) = 1.5, which means that hydroiodic acid has a(n)
________________.
1.
2.
3.
4.
low boiling point
low acidity
unstable gas phase
dipole moment
Copyright © Cengage Learning. All rights reserved.
12 | 16
ANSWER
Choice #4 associates the bond polarity of a diatomic molecule
with having a dipole moment.
Copyright © Cengage Learning. All rights reserved.
12 | 17
QUESTION
If we consider the electron configuration of strontium, [Kr]5s2,
and that of oxygen, [He]2s22p4, both atoms will attain stable
noble gas electron configurations by the transfer of ____
electron(s). This will give Sr a charge of ___ and O a charge of
___. Hence the ionic compound formed has the formula
___________ and is named strontium oxide.
1.
2.
3.
4.
1 ; 1+ ; 1– ; SrO
2 ; 2+ ; 2– ; SrO
2 ; 2+ ; 1– ; SrO
2 ; 2– ; 2+ ; SrO
Copyright © Cengage Learning. All rights reserved.
12 | 18
ANSWER
Choice #2 correctly indicates the transfer of two electrons from
strontium to oxygen to form the ionic compound known as
strontium oxide.
Copyright © Cengage Learning. All rights reserved.
12 | 19
QUESTION
What is the expected ground state electron configuration for Te2–?
1.
2.
3.
4.
[Kr]5s24d105p4
[Kr]5s24d104f145p6
[Kr]5s24d105p6
[Ar]5s24d105p2
Copyright © Cengage Learning. All rights reserved.
12 | 20
ANSWER
Choice #3 is the correct answer. Te2– contains 54 electrons and
has the noble gas configuration of Xe.
Copyright © Cengage Learning. All rights reserved.
12 | 21
QUESTION
What is the correct electron configuration for the most stable form
of the sulfur ion in an ionic compound?
1.
2.
3.
4.
1s22s22p63s2
1s22s22p63s23p2
1s22s22p63s23p4
1s22s22p63s23p6
Copyright © Cengage Learning. All rights reserved.
12 | 22
ANSWER
Choice #4 is the correct answer. S2– is the most stable form of the
sulfur ion in an ionic compound. It contains 18 electrons and has
the noble gas configuration of Ar.
Copyright © Cengage Learning. All rights reserved.
12 | 23
QUESTION
The structures of ionic compounds are usually described as the
packing of ____________ with smaller ____________ fitting
into the interstices.
1.
2.
3.
4.
anions; cations
anions; electrons
cations; anions
cations; electrons
Copyright © Cengage Learning. All rights reserved.
12 | 24
ANSWER
Choice #1 correctly describes the packing of anions (which tend
to be larger) into specific patterns known as crystal lattices, while
cations fit into the spaces or interstices between the packed
anions.
Copyright © Cengage Learning. All rights reserved.
12 | 25
QUESTION
Rank the following from smallest to largest atomic radius:
Ar, S2–, Ca2+, K+, Cl–
1.
2.
3.
4.
Ar < K+ < Ca2+ < S2– < Cl–
Ca2+ < K+ < Ar < Cl– < S2–
Ar < Cl– < S2– < Ca2+ < K+
S2– < Cl– < Ar < K+ < Ca2+
Copyright © Cengage Learning. All rights reserved.
12 | 26
ANSWER
Choice #2 is the correct answer. They all have the same electron
configuration of the noble gas Ar. Therefore, nuclear charge
becomes very important in determining the sizes relative to each
other. The higher the nuclear charge, the smaller the ion/atom.
Copyright © Cengage Learning. All rights reserved.
12 | 27
QUESTION
Which atom or ion has the smallest radius?
1.
2.
3.
4.
O2+
O+
O
O2–
Copyright © Cengage Learning. All rights reserved.
12 | 28
ANSWER
Choice #1 is the correct answer. As electrons are removed, the
effective nuclear charge has a stronger effect and thus makes the
ion, O2+, the smallest.
Copyright © Cengage Learning. All rights reserved.
12 | 29
QUESTION
Which of the following has the lowest ionization energy?
1.
2.
3.
4.
Se2–
Br–
Sr2+
Rb+
Copyright © Cengage Learning. All rights reserved.
12 | 30
ANSWER
Choice #1 is the correct answer. Se2– has the smallest effective
nuclear charge and thus does not bind the electrons as strongly as
the others.
Copyright © Cengage Learning. All rights reserved.
12 | 31
QUESTION
Lewis structures show the arrangement of ________electrons in
an atom or ion.
1.
2.
3.
4.
all
core
valence
missing
Copyright © Cengage Learning. All rights reserved.
12 | 32
ANSWER
Choice #3 correctly indicates that only valence electrons are
included in Lewis structures.
Copyright © Cengage Learning. All rights reserved.
12 | 33
QUESTION
In the Lewis structure for H2S there are a total of ______
electrons and ____ pair(s) of nonbonding electrons.
1.
2.
3.
4.
9;2
9;1
8;2
8;1
Copyright © Cengage Learning. All rights reserved.
12 | 34
ANSWER
Choice #3 correctly describes the Lewis structure for
hydrosulfuric acid: (6 electrons from S) + (2 × 1 = 2 electrons
from H) = 8 total electrons. The Lewis structure is the same as
that for H2O, with S in place of O.
Copyright © Cengage Learning. All rights reserved.
12 | 35
QUESTION
The Lewis structure for SO2 contains ____ total electrons
and____ nonbonding pairs of electrons, as well as one ______
bond and one _______ bond between the central sulfur and the
oxygen atoms.
1.
2.
3.
4.
16 ; 4 ; single ; double
16 ; 6 ; single ; double
18 ; 4 ; single ; triple
18 ; 6 ; single ; double
Copyright © Cengage Learning. All rights reserved.
12 | 36
ANSWER
Choice #4 correctly describes the SO2 molecule with (3 × 6 =) 18
electrons and S located between the two O’s with one single and
one double bond.
Copyright © Cengage Learning. All rights reserved.
12 | 37
QUESTION
Consider the following compounds:
CO2
N2 CCl4
Which compound exhibits resonance?
1.
2.
3.
4.
CO2
N2
CCl4
At least two of the above compounds exhibit resonance.
Copyright © Cengage Learning. All rights reserved.
12 | 38
ANSWER
Choice #1 is the correct answer. Only CO2 exhibits resonance.
Copyright © Cengage Learning. All rights reserved.
12 | 39
QUESTION
Which of the following supports why Lewis structures are not a completely
accurate way to draw molecules?
1.
2.
3.
4.
We cannot say for certain where an electron is located yet when drawing
Lewis structures, we assume the electrons are right where we place them.
When adding up the number of valence electrons for a molecule, it is
possible to get an odd number which would make it impossible to satisfy
the octet rule for all atoms.
Both statements 1 and 2 above support why Lewis structures are not a
completely accurate way to draw molecules.
Lewis structures are the most accurate way to draw molecules and are
completely correct.
Copyright © Cengage Learning. All rights reserved.
12 | 40
ANSWER
Choice #3 is the correct answer.
Copyright © Cengage Learning. All rights reserved.
12 | 41
QUESTION
It is important to fully understand that Lewis structures are useful
in determining the bonding relationships between atoms in a
molecule, but that they do not directly provide a true picture of
molecular shape. While the Lewis structure for methane, CH4, an
important greenhouse gas, suggests a flat structure with 4
hydrogens arranged around a central carbon, the methane
molecule is actually ________.
1.
2.
3.
4.
square planar
trigonal
tetrahedral
octahedral
Copyright © Cengage Learning. All rights reserved.
12 | 42
ANSWER
Choice #3 correctly describes the methane molecule as a
tetrahedron, with the carbon centrally located in the geometric
center and the 4 hydrogens forming the corners of the
tetrahedron.
Copyright © Cengage Learning. All rights reserved.
12 | 43
QUESTION
While the electron pair geometry of NH3 is _______, VSEPR
predicts the molecular shape as _________, due to the pair of
nonbonding electrons on the central N.
1.
2.
3.
4.
tetrahedral; trigonal pyramidal
trigonal planar; tetrahedral
tetrahedral; trigonal planar
Both are trigonal planar.
Copyright © Cengage Learning. All rights reserved.
12 | 44
ANSWER
Choice #1 answers both geometry questions correctly. The
central N has four pairs of electrons around it, giving it a
tetrahedral electron pair geometry. But because one of the corners
of the tetrahedron is an electron pair, the molecule is a trigonal
pyramid with the N forming the apex and the three H’s forming
the pyramidal base.
Copyright © Cengage Learning. All rights reserved.
12 | 45
QUESTION
Draw the Lewis structures for the following compounds:
CBr2H2
BH3
HCl
Which compound has bond angles of 109.5˚ around the central
atom?
1.
2.
3.
4.
BH3
CBr2H2
HCl
At least two of the above compounds have bond angles of
109.5˚.
Copyright © Cengage Learning. All rights reserved.
12 | 46
ANSWER
Choice #2 is the correct answer. CBr2H2 is tetrahedral, BH3 is
trigonal planar, and HCl is linear.
Copyright © Cengage Learning. All rights reserved.
12 | 47
QUESTION
In determining the shape of the SO2 molecule we examine the
Lewis structure and find the central S atom attached to O’s via
one single and one double bond. The electron pair geometry is
_______ and the molecular geometry is _________, with bond
angles of ____ degrees.
1.
2.
3.
4.
trigonal planar ; linear ; 180
trigonal planar ; bent ; 120
tetrahedral ; linear ; 120
tetrahedral ; trigonal planar ; 120
Copyright © Cengage Learning. All rights reserved.
12 | 48
ANSWER
Choice #2 correctly describes the electron pair about the central S
as trigonal planar. S has one nonbonding electron pair, a single
bond, and a double bond (counts as a single bond for shape).
Because one corner of the triangle is occupied by an electron
pair, the molecule has a bent shape with bond angles of 120o.
Copyright © Cengage Learning. All rights reserved.
12 | 49
QUESTION
Draw the Lewis structures for the following compounds:
HCN
NH4+
NO2–
Which compound has bond angles of 120˚ around the central
atom?
1.
2.
3.
4.
HCN
NH4+
NO2–
At least two of the above compounds have bond angles of
120˚.
Copyright © Cengage Learning. All rights reserved.
12 | 50
ANSWER
Choice #3 is the correct answer. NO2– has trigonal planar electron
pair geometry. NH4+ has tetrahedral electron pair geometry and
HCN has linear electron pair geometry.
Copyright © Cengage Learning. All rights reserved.
12 | 51
QUESTION
How many of the following statements are true regarding the molecule SeO2?
I. The electron pair geometry of the molecule is trigonal planar.
II. The molecular structure of the molecule is linear.
III. The number of effective pairs around the central atom is four.
1.
2.
3.
4.
0
1
2
3
Copyright © Cengage Learning. All rights reserved.
12 | 52
ANSWER
Choice #2 is the correct answer. Only statement I is true. SeO2
has trigonal planar electron pair geometry, bent molecular
structure, and three effective pairs around the central atom S.
Copyright © Cengage Learning. All rights reserved.
12 | 53