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CHEMICAL BONDING REVIEW
Student Review Packet Answer Key
1. Fill in the letters in the acrostic with a vocabulary word or phrase. The letters may
appear at the beginning of the word/phrase, in the middle of the word/ phrase, or at
the end of the word/phrase. Then, on the lines below, define each word/phrase using
your own words.
Answers may vary.
cheMical bonds
dip Ole
Lone electron pair
b Ent
Covalent bond
do Uble covalent bond
po Lar molecule
lineAr
py Ramidal
electroneGativity
tetrahEdral
b Ond angle
sym Metrical
valence Electrons
central aTom
te Rminal atoms
as Ymmetrical
Definitions:
a) chemical bonds – forces that hold atoms together in molecules and keep ions in place in solid ionic
compounds
b) dipole – a molecule that has two electrically charged regions (poles)
c)
lone electron pair – nonbonding pair of electrons assigned exclusively to one atom in a Lewis structure
d) bent – 3-dimensional molecular shape in which two nonbonding electron pairs repel the bonding
electron pairs, pushing them closer together to give a bond angle of 104.5 
e)
covalent bond – type of bond formed when a pair of electrons are shared between two bonded atoms
f)
double covalent bond – two pairs of electrons are shared by two bonded atoms
g) polar molecule – a molecule in which there is a separate region of positive and negative charge;
one or more atoms is slightly negative and one or more atoms is slightly positive is such a way
that the bond polarities do not cancel
h) linear – 3-dimensional molecular shape in which the bond angle between the terminal atoms is 180 
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CHEMICAL BONDING REVIEW
i)
pyramidal – 3-dimensional molecular shape in which the nonbonding electron pair repels the bonding
electron pairs, pushing them closer together to give a bond angle of 107 
j)
electronegativity – tendency for an atom to attract electrons to itself when it is chemically combined
with another element
k)
tetrahedral – 3-dimensional molecular shape in which the bond angle is 109.5
l)
bond angle – the angle formed between two terminal atoms in a molecule
m) symmetrical – a molecule in which the bond polarities cancel
n) valence electrons – electrons in the highest occupied energy level of an atom; electrons that may
participate in bonding
o) central atom – an atom bonded to two or more atoms in a structure
p) terminal atoms – atoms bonded only to one other atom in a structure
q) asymmetrical – a molecule in which the bond polarities do not cancel
2. Explain the importance of valence electrons.
Valence electrons are the electrons in the highest occupied energy level of an atom. They are usually the
only electrons used in the formation of chemical bonds. The number of valence electrons corresponds to
the Family (Group) number in the Periodic Table and defines the chemical properties of an element
3. What is the relationship between the electron dot structure of an element and the
location of the element in the Periodic Table?
The number of electrons in the electron dot structure of an element is the same as the Family (Group)
number for the representative elements.
4. How many electrons must be gained or lost by each atom to achieve a stable electron
configuration?
a) N
3 gained
d) Mg 2 lost
b) Cl
1 gained
e) Al
c) S
2 gained
f) P
3 lost
3 gained
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CHEMICAL BONDING REVIEW
5. Complete the Table by drawing the Lewis (electron) dot structures.
LEWIS DOT STRUCTURES
b) N
c) O
a) Al
Al
N
e) O2
d) KCl
O
f) H2S
K Cl
g) CH4
h) HCN
H
O
O
H S
H C
H
C
N
H
H
H
6. Why do elements form chemical bonds?
Elements form chemical bonds to achieve the stable electron configuration of a noble gas.
7. Compare covalent bonds, ionic bonds, and hydrogen bonds.
An ionic bond forms when there is an attraction between an anion and a cation due to the transfer of
electrons.
A covalent bond results when atoms share electrons to gain the electron configuration of a noble gas.
A hydrogen bond is a weak attractive force in which hydrogen that is covalently bonded to a very
electronegative element is also weakly bonded to a lone (nonbonding) electron pair of another
electronegative element.
8. Differentiate between polar covalent and nonpolar covalent bonds.
A polar covalent bond is a bond formed between two different atoms and the bonding electrons are shared
unequally.
A nonpolar covalent bond forms when the atoms involved in the bond are alike and the bonding electrons
are shared equally.
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9. Characterize each bond as nonpolar covalent, polar covalent, or ionic; then, arrange
the bonds in order of increasing ionic character.
a) K  O
____ionic bond______
b) Li  F
____ionic bond______
c) C  H
__polar covalent bond_
d) N  N
nonpolar covalent bond
e) Cl  F
_polar covalent bond_
NN
CH
ClF
KO
LiF
Bonds arranged in order of increasing ionic character
10. Compare the physical and chemical characteristics of metals and ionic compounds.
Both metals and ionic compounds are composed of ions held together by electrostatic bonds. Ionic
compounds are composed of positive and negative ions packed together in an orderly arrangement to form
crystalline solids; metals are composed of stationary cations surrounded by a sea of free-floating valence
electrons. Metals always conduct electricity (due to the mobility of electrons); ionic compounds only
conduct a current when melted or dissolved in water. Metals are malleable and ductile; ionic compounds
are brittle. Like ionic compounds, metals are crystalline solids.
11. How many electron pairs do two atoms in a triple covalent bond share?
3 electron pairs
12. What determines which atom monopolizes the shared electron pair(s) involved in a
bond?
The electronegativity values of the two atoms involved in a bond determine which of the two atoms
monopolizes the shared electron pair(s). The greater the electronegativity of an atom in a bond, the more
strongly it attracts the electrons in a covalent bond.
13. Distinguish between a nonpolar bond and a nonpolar molecule.
A nonpolar bond forms when the atoms in a molecule are alike and the bonding electrons are shared
equally.
A nonpolar molecule is a symmetrical molecule in which the bond polarities cancel. This occurs when
there are no nonbonding electron pairs and the terminal atoms are alike.
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14. Outline a procedure that could be used to accurately predict the shape of a molecule
containing covalent bonds.
1.
2.
3.
Write the Lewis structure for the molecule.
Count the number of nonbonding electron pairs and bonding electron pairs around the
central atom.
Predict the shape of the molecule using the following chart:
MOLECULAR SHAPE
# Nonbonding
Electron Pairs
2
1
0
0
0
# Bonding
Electron Pairs
2
3
4
3
2
Predicted
Molecular Shape
Bent
Pyramidal
Tetrahedral
trigonal planar
Linear
15. Complete the chart summarizing the molecular geometries based on VSEPR theory.
MOLECULAR GEOMETRIES
Geometric
# Electron
#Nonbonding
Bond
Example
Shape
Pair Sites
Electron Pairs
Angle
pyramidal
4
1
107
NH3, PH3
bent
4
2
104.5
H2O
tetrahedral
4
0
109.5
SiCl4
linear
2
0
180
CO2
3
0
120
BH3
Trigonal planar
16. How do shape and symmetry influence the polarity of a molecule? Support your
answer citing specific examples.
The shape and symmetry of a molecule determine whether or not its bond polarities cancel. If the bond
polarities cancel, the molecule is a nonpolar molecule; if the bond polarities do not cancel, the molecule is
a polar molecule. A molecule that has a tetrahedral, linear, or trigonal planar shape is polar if the
terminal atoms are not all the same (the bond polarities do not cancel, the molecule is asymmetrical) but is
nonpolar if the terminal atoms are the same (the bond polarities cancel, the molecule is symmetrical). A
molecule with nonbonding electron pairs is asymmetrical; therefore, it is a polar molecule.
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17. Complete the following table.
Formula
COMMON COVALENT COMPOUNDS
Lewis
VSEPR
Molecular
Bond
Structure
Model
Shape
Angle
H2
H---H
H---H
H O
H
H2 O
H
H
N
H
NH3
H
Cl
C
H
H
N
N
F
B
BF3
CF4
F
C
F
F
H
H
Cl
F
O
O
O
C
C
O
O
C
104.5
polar
molecule
pyramidal
107
polar
molecule
tetrahedral
109.5
polar
molecule
linear
180
nonpolar
molecule
trigonal planar
120
nonpolar
molecule
tetrahedral
109.5
nonpolar
molecule
trigonal planar
120
nonpolar
molecule
pyramidal
107
polar
molecule
bent
104.5
polar
molecule
linear
180
nonpolar
molecule
linear
180
nonpolar
molecule
bent
104.5
polar
molecule
linear
180
nonpolar
molecule
S
F
S
F
F
H
O
Na
O
C
Cl
Na
O
O
SF2
bent
H
Cl
Na
O
nonpolar
molecule
P
Cl
P
Na
O2
180
H
Cl
Na2O
F
Al
H
linear
F
B
F
F
Al
Cl
C2H2
N
F
F
H
H
H
N
F
F
C
PCl3
CO2
Cl
C
F
F
H
H
H
H
N2
N
H
H
CH3Cl
AlH3
O
Polar or
Nonpolar
H
H
C
C
H
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CHEMICAL BONDING REVIEW
18. Construct a Venn diagram to compare and contrast each pair of molecules. Be sure
to include information about molecular shape, bond angle between the terminal
atoms, bond character, and molecular polarity.
a) CH4 and CH2Cl2
CH4
CH2Cl2
-tetrahedrons
- nonpolar
molecule
-polar molecule
- bond angle=
109.5º
-4 covalent
bonds
b) H2Se and PH3
H2Se
PH3
-bent shape
-2 bonding and 2 nonbonding
electron pairs around the
central atom
-bond angle = 104.5 º
-asymmetrical
shape
-bonding and
numbering
electron pairs
-covalent bonds
-polar molecules
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-pyramidal shape
-3 bonding and 1
nonbonding electron pair
around the central atom
-bond angle = 107 º
CHEMICAL BONDING REVIEW
19. Ammonia molecules undergo hydrogen bonding with water.
a) Diagram the formation of the hydrogen bond between one molecule of ammonia
and one molecule of water. Label the hydrogen bond.
Hydrogen bond
H
H
N
H
H
O
H
b) Would you expect methane, CH4, to participate in hydrogen bonding? Why?
No. The hydrogen atoms are not bonded to a very electronegative element.
20. Summarize the types of attractions between atoms by completing the flowchart.
Give a brief description and an example of each attractive force.
Attractions between Atoms

____________________________________________________


Intramolecular Attractions
Intermolecular Attractions
Attractions within molecules
Attractions between molecules
1) Ionic bond
1) van der Waals Forces
an electrostatic attraction between
oppositely charged ions
describes the weakest
intermolecular attraction
a) dispersion force
weakest intermolecular
attraction caused by the
motion of electrons
2) Covalent bond
b) dipole interaction
bond formed between two atoms
that share electrons
weak intermolecular force
that results from the attraction
of oppositely
charged regions of polar
molecules
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CHEMICAL BONDING REVIEW
3) Metallic bond
2) Hydrogen bonding
force of attraction that holds
metals together; the attraction
of free-floating valence electrons
for positively charged metal ions
attractive force in which a
hydrogen atom covalently
bonded to an electronegative
element is also weakly attracted
to the electronegative element in
another molecule
21. Rank these attractive forces from strongest to weakest: covalent bond, hydrogen
bond, ionic bond, van der Waals forces.
ionic bond
covalent bond
hydrogen bond
Strongest
van der Waals forces
Weakest
22. Read each of the statements below. Decide if the statement is true or false; if the
statement is false, change the underlined word or phrase to make the statement
true.
_F_
a) Ionic bonds form as the result of electron sharing. Covalent
_F_
b) A barometer is used to measure the melting point of a solid. thermometer
_T_
c) Elements form bonds to achieve a stable octet.
_F_
d) Molecular compounds generally have high melting points and conduct a
current when dissolved in water. Ionic
_F_
e) The degree of polarity between any two atoms is determined by
consulting the Periodic Table. Electronegativity Table
_F_
f) Two electrons are shared in a double covalent bond. electron pairs
_F_
g) A polar bond is a dipole. molecule
_T_
h) When atoms are joined by a covalent bond and the bonding electrons
are shared equally, the bond is nonpolar.
_F_
i) VSEPR Theory states that molecules adjust their 3-dimensional shapes
so that the valence electron pairs around the central atom are uniformly
distributed. as far apart as possible
_F_
j) Crayon, a nonpolar substance, is soluble in water. Carbon tetrachloride or any
nonpolar solvent
_T_
k) Boron trifluoride, BF3, is a nonpolar molecule containing polar bonds.
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23. Use the vocabulary below to explain and justify the predicted molecular shape and
polarity of sodium oxide, Na2O.
..
Na  O :

Na
asymmetrical
bent
bond angle
central atom
lone electron pair(s)
polar
separate regions of charge
terminal atom(s)
VSEPR theory
According to VSEPR Theory, the two lone electron pairs around the central atom strongly repel the
bonding electron pairs pushing them closer together. The experimentally measured bond angle between
the terminal atoms is 104.5, and the shape of the molecule is bent. Bent molecules are asymmetrical.
They have separate regions of positive and negative charge, resulting in a polar molecule.
24. How does molecular polarity influence the ability of a substance to dissolve in
another substance?
Polar and ionic substances dissolve in polar solvents; nonpolar substances dissolve in nonpolar
substances.
25. Predict whether or not sodium sulfate (Na2SO4) would be expected to dissolve in
each of these solvents. Justify each prediction.
a) ammonia (NH3)
Prediction: Sodium sulfate will dissolve in ammonia.
Justification: Sodium sulfate is an ionic compound; ammonia is a polar solvent.
Ionic compounds dissolve in polar solvents.
b) water (H2O)
Prediction: Sodium sulfate will dissolve in water.
Justification: Sodium sulfate is an ionic compound; water is a polar solvent.
Ionic compounds dissolve in polar solvents.
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c) carbon tetrachloride (CCl4)
Prediction: Sodium sulfate will not dissolve in carbon tetrachloride.
Justification: Sodium sulfate is an ionic compound; carbon tetrachloride is a nonpolar solvent. Ionic compounds will not dissolve in nonpolar
solvents,
26. Would your predictions in Question 25 remain the same if methane (CH4) were used
instead of sodium sulfate? Explain.
No. Methane is a nonpolar molecule. Nonpolar molecules dissolve in nonpolar solvents (carbon
tetrachloride). Nonpolar molecules do not dissolve in polar solvents (ammonia, water).
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