Review Questions
1.
Draw the electron dot structure for the following diatomic halogen molecules.
a) chlorine
b) iodine
..
..
:Cl : Cl:
··
··
.. ..
:I : I:
·· ··
2.
Draw the electron dot structure for the following covalent molecules:
a) H2S
b) PH3
c) BrF
..
:S:H
··
H
··
H:P:H
··
H
..
..
:Br : F:
·· ··
3.
Draw the electron dot structure for the polyatomic ions (a) NH4+
H +
··
H :N: H
··
H
(b) H3O +
H +
··
H:O:H
··
4.
Explain the difference between a nonpolar covalent bond and a polar covalent bond.
Nonpolar covalent bond occurs when there is an equal or almost equal sharing of bonding
electrons ΔEN is less than 0.4.
Polar covalent bond occurs when there is an unequal sharing of bonding electrons ΔEN is greater
than 0.4 and less than 1.7.
5.
Use electronegative differences to identify the types of bonds between atoms in the following
pairs of elements (ionic, polar covalent or nonpolar covalent).
a) H and Cl
2.2 3.16 ΔEN = 0.96 polar
b) K and Cl
0.82 3.16 ∆EN = 2.34 ionic
c) N and O
3.04 3.44 ∆EN = 0.4 nonpolar
d) I and F
2.66 3.98 ∆EN =1.32 polar
e) Br and Br
2.96 2.96 vEN = 0 nonpolar
6.
Which covalent bond is the most polar and which is the least polar?
a) H – Cl
b) H – Br
c) H – S
d) H – C
2.20 3.16
2.02 2.96
2.20 2.58
2.20 2.55
∆EN = 096
∆EN = .76
∆EN = 0.38
∆EN = 0.35
Most polar
e) F – F
3.98 3.98
∆EN = 0
least polar
7.
Explain why the noble gasses are monatomic but the halogens are diatomic molecules.
The noble gasses are monatomic because they have full (stable) valence shells. The halogens
are diatomic molecules because they get a full valence by each offering a bonding electron to
form a shared pair of electrons.
8.
Draw the electron dot structure for each of the following:
a) H2O
b) H2O2
c) PCl3
d) NH3
..
:O:H
··
H
.. ··
H :O:O:H
·· ··
.. .. ..
:Br : P : Br:
·· ·· ..
:Br :
··
··
H :N: H
··
H
9.
Classify the following compounds as ionic or covalent.
a) H2S
b) Na2S
c) HCl
d) MgCl2
Covalent
ionic
covalent
ionic
nonmetals
metal-nonmetal nonmetals
metal - nonmetal
10.
Explain why atoms form chemical bonds and describe the difference between an ionic bond
and a covalent bond.
Atoms form chemical bonds with valence electrons so that they can achieve a full shell.
Ionic bonds occur when valence electrons are lost by the metals and gained by the nonmetal.
Covalent bonding occurs when valence electrons are shared between the atoms and ownership
of the valence electrons are maintained between the atoms.
11.
12.
State the number of electrons shared by two atoms in a:
a) single covalent bond
b) double covalent bond
1 pair – 2 electrons
2 pair – 4 electrons
c) triple covalent bond
3 pair – 6electrons
Draw electron dot structures for the following molecules:
a) I2
b) OF2
c) H2S
d) NI3
e) HCN
a)
.. ..
:I : I:
·· ··
b)
.. ..
:O:F:
·· ··
:F:
..
c)
..
:S:H
··
H
d)
.. ·· ..
:I : N : I :
·· ·· ··
: I:
··
e)
H:C:::N
-
13.
Explain how the VSEPR theory can be used to predict the shapes of molecules.
4 pairs of bonding electrons – tetrahedral (bonding angle = 109.5)
3 pairs of bonding electrons and 1 lone pair – pyramidal (bonding angle = 107)
2 pairs of bonding electrons and 2 lone pairs – bent (bonding angle = 105)
1 pair of bonding electrons and 3 lone pairs linear (bonding angle = 180)
14.
Use VSEPR theory to predict the bond angles in:
a) methane (CH4)
b) ammonia (NH3)
c) water (H2O)
109.5
107
105
15.
Use VSEPR theory to predict the shapes of the following:
a) SCl2
b) CO2
c) SiCl4
d) H2S
Bent
linear
tetrahedral
bent
e) PH3
pyramidal
16.
The bonds between the following pairs of elements are covalent. Arrange them according to
polarity, the most polar to the least polar.
a) H – Cl
b) C – H
c) H – F
d)H – O
e) H – H
f) S – Cl
2.20 3.16
2.55 2.20
2.20 3.98
2.20 3.44
2.20 2.20
2.58 3.16
∆EN= 0.96
0.35
1.78
1.24
0
0.58
17.
BONUS
Based on molecular shapes and polarity of bonds, which of the following molecules are polar
molecules?
a) SO2
b) H2S
c) BF3
d) SBr2
e) HCl
bent
bent
pyramidal
bent
linear
∆EN=
2.58 3.44
2.20 2.58
2.04 3.98
2.58 2.96
2.02 3.16
∆EN=
0.86
0.38
1.94
0.38
0.96
Bonds
polar
nonpolar
polar
nonpolar
polar
molecule Polar
nonpolar
nonpolar
nonpolar
polar
18.
Write the correct formula for:
1) dinitrogen monoxide
__ N2O ______
2) nitrogen trifluoride
___ NF3______
3) carbon dioxide
__ CO2_______
4) diphosphorous pentoxide
__ P2O5______
5) sulfur dioxide
___ SO2_____
6) silicon tetrachloride
___ SiCl4_____
7) silicon dioxide
____ SiO2_____
8) dinitrogen pentasulfide
___ N2S5______
9) carbon monoxide
___CO_______
10) nitrogen monoxide
___NO______
Write the correct name for:
1) N2O3
______
2) NI3
____
dinitrogen trioxide ______
nitrogen triiodide ______
3) SF6
____
sulfur hexafluoride _______
4) CO
_____
5) P2O5
____
diphosphorous pentoxide ____
6) SO2
____
sulfur dioxide ____
7) SiO2
____
silicon dioxide _____
8) N2S5
___
9) CO2
____
carbon dioxide _______
10) PF3
____
phosphorous trifluoride ______
carbon monoxide _______
dinitrogen pentasulfide _______