Regents Chemistry
2013-2014
Unit Test Review: Covalent Bonding
1. A covalent chemical bond is defined as two atoms chemically combining by sharing
electrons.
2. In order to break a chemical bond energy must be absorbed (endothermic process); in order to
form a chemical bond energy must be released (exothermic process).
3. A covalent bond is formed between these types of elements: non-metal elements only
4. List the properties of covalent substances and contrast to the properties of ionic substances:
covalent substances:
 low mp, low bp, low Hf, low Hv, hi VP
 poor conductors of heat & electricity
 soft, crumbly solids
ionic substances:
⦁ hi mp, hi bp, hi Hf, hi Hv, low VP
⦁ good conductors of heat & electricity
⦁ hard, rigid solids
5. Draw Lewis Dot structures for the following covalent compounds:
6.
7.
CO2
H2O
HCl
O2
CHI3
C2H6
NH3
SO3
A non-polar covalent bond is: bond between two non-metal atoms in which electrons are
evenly distributed
A polar covalent bond is: bond between two non-metal atoms in which electrons are
unevenly distributed
8. How to determine if a covalent bond is polar or not:
o electronegativity difference of 0 to 0.5 generally indicates a non-polar bond
o electronegativity difference of >0.5 to <1.7 generally indicates a polar bond
o electronegativity difference of >1.7 generally indicates a(n) covalent bond
o The higher the electronegativity difference in a bond the greater the ionic character of
the bond
o The lower the electronegativity difference in a bond the greater the covalent character
of the bond
bond
(electroneg values)
polarity
(yes/no)
bond type
(NPC/PC/I)
bond
(electroneg values)
polarity
(yes/no)
bond type
(NPC/PC/I)
a
C-H
2.6 2.2
0.4
No
NPC
j
C-Cl
2.6 3.2
0.6
Yes
PC
b
N-N
3.0 3.0
0
No
NPC
k
C-F
2.6 4.0
1.4
Yes
PC
c
C-N
2.6 3.0
0.4
No
NPC
l
H-H
2.2 2.2
0
No
NPC
d
H-Cl
2.2 3.2
1.0
Yes
PC
m
S-O
2.6 3.4
0.8
Yes
PC
e
C-O
2.6 3.4
0.8
Yes
PC
n
Ca-H
1.0
2.2
1.2
Yes
I
f
H-O
2.2 3.4
1.2
Yes
PC
o
Na-Br
0.9 3.0
2.1
Yes
I
g
H-F
2.6 4.0
1.4
Yes
PC
p
Cs-I
0.8 2.7
1.9
Yes
I
h
H-N
2.2 3.0
0.8
Yes
PC
q
Ca-F
1.0
4.0
3.0
Yes
I
9. In a single covalent bond ONE pair(s) of electrons are shared between two atoms; in a double
covalent bond TWO pair(s) of electrons are shared between two atoms; in a triple covalent bond
THREE pair(s) of electrons are shared between two atoms;
10. The rules for assigning oxidation numbers are:
o 1. Oxidation # for free, uncombined elements is zero
o 2. Oxidation # for monatomic ions is equal to the charge of the ion
o 3. Fluorine is always -1
o 4. Hydrogen is nearly always +1, except when bonded to metal, then is -1
o 5. Oxygen is nearly always -2 except: bonded to F then is +1; in peroxide ion is -1
o 6. Sum of all oxidation numbers in neutral compound is zero
o 7. Sum of all oxidation numbers in polyatomic ion equals charge of ion
11. Name the following covalent compounds using both the stock & the traditional naming
systems:
1
CO2
traditional system name
carbon dioxide
stock system (roman #) name
carbon (IV) oxide
2
CO
carbon monoxide
carbon (II) oxide
3
SO2
sulfur dioxide
sulfur (IV) oxide
4
SO3
sulfur trioxide
sulfur (VI) oxide
5
N2O
dinitrogen monoxide
nitrogen (I) oxide
6
NO
nitrogen monoxide
nitrogen (II) oxide
7
N2O3
dinitrogen trioxide
nitrogen (III) oxide
8
NO2
nitrogen dioxide
nitrogen (IV) oxide
9
N2O4
dinitrogen tetroxide
nitrogen (IV) oxide
10
N2O5
dinitrogen pentoxide
nitrogen (V) oxide
11
PCl5
phosphorus pentachloride
phosphorus (V) chloride
12
PCl3
phosphorus trichloride
phosphorus (III) chloride
13
NH3
nitrogen trihydride
nitrogen (III) hydride
14
SCl6
sulfur hexachloride
sulfur (VI) chloride
15
P2O5
diphosphorus pentoxide
phosphorus (V) oxide
16
CCl4
carbon tetrachloride
carbon (IV) chloride
17
SiO2
silicon dioxide
silicon (IV) oxide
18
CS2
carbon disulfide
carbon (IV) sulfide
19
CF2
carbon difluoride
carbon (II) sulfide
20
PBr3
phosphorus tribromide
phosphorus (III) bromide
12. Write the correct covalent formulas from the compound names
a.
iron (II) oxide
FeO
b. iron (III) oxide
c.
Fe2O3
carbon monoxide
CO
d. calcium chloride
CaCl2
e.
potassium nitrate
KNO3
f.
magnesium hydroxide
g.
aluminum sulfate
Mg(OH)2
Al2(SO4)3
h. copper (II) sulfate
CuSO4
i.
lead (IV) chromate
Pb(CrO4)2
j.
diphosphorus pentoxide
P2O5
k.
potassium permanganate
KMnO4
l.
sodium hydrogen carbonate
m. zinc nitrate
NaHCO3
Zn(NO3)2
n.
aluminum sulfite
Al2(SO3)3
o.
phosphorus pentabromide
p.
carbon tetrachloride
CCl4
q.
diarsenic pentoxide
As2O5
r.
diphosphorus trioxide
P2O3
s.
carbon (IV) selenide
CSe2
t.
arsenic (III) chloride
AsCl3
u.
phosphorus (V) sulfide
P2S5
v.
silicon (IV) oxide
PBr5
SiO2
Molecular shapes of covalent molecules:
There are five molecular shapes you need to know. What are they? Give an example for each.
1. linear
CO2
2.
bent
H 2O
3.
trigonal planar
4.
triagonal pyramidal
5.
tetrahedral
BF3
NH3
CH4
Covalent Bonding verses Ionic Bonding:
Use the following terms and write a paragraph to explain each statement below.
 electronegativity of elements involved
 electrostatic attraction occurs between what entities
 type(s) of elements in each bond
 IMF between neighboring molecules
1. describe the process involved in forming a covalent bond(s) which results in a covalent
molecule or a covalent compound
non-metal atoms have fairly strong electronegativity values but there is not enough
of a difference in their electronegativity values for a transfer of valence electrons
to occur from one non-metal atom to another non-metal atom so instead the nonmetal atoms share electrons in single, double or triple bonds to fulfill the octet
rule
2. describe the two step process involved in forming an ionic bond which results in
formation of an ionic compound
1st step: non-metal atoms have much stonger electronegativity values than metals
therefore the non-metal atoms take away the metal valence electrons. This
transfer of valence electrons from metal atom to non-metal atom results in the
formation of positive metal ions (lose electrons) and negative non-metal ions (gain
electrons)
2nd step: oppositely charged ions (+ metal ions & - non-metal ions) are
electrostatically attracted together in an ionic bond
Review questions at the end of the review packet:
Q#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
answer
4
2
1
2
2
3
1
2
3
3
4
3
3
1
4
Q#
16
17
18
19
20
21
22
23
24
answer
1
2
3
2
3
2
4
2
1
Q#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
answer
4
2
3
2
3
2
4
2
3
4
3
3
3
3
?
Q#
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
answer
3
4
1
3
1
2
3
1
2
2
4
2
3
3
2