Chemistry 521
Chapter 14 Assignment
Name:______Answer Key________________
PART I. Fill in the Blanks.
When atoms share electrons to gain the stable electron
configuration of a noble gas, the bonds formed are called __1__
bonds. One shared pair of valence electrons constitutes a __2__
covalent bond. Two shared pairs constitutes a __3__ covalent
bond. Three shared pairs constitutes a __4__ covalent bond. In
some cases, one of the atoms in the bond provides both electrons in
the bond; this is a __5__ covalent bond.
One type of structural formula that is commonly used to show
the bonds and unshared pairs of electrons in a molecule is called the
__6__. However, this type of structure does not indicate the 3
dimensional arrangement of the atoms. As a general rule,
molecules adjust their 3D shapes so that the valence electron pairs
around a central atom are as far apart as possible. This guiding
principle is known as the __7__ theory and can be used to predict
the 3D shapes of molecules.
There are some exceptions to the octet when drawing Lewis
Structures. Molecules that have an unpaired electron and are
therefore attracted by magnetic field are called __8__. Central
atoms like S and P which are capable of having more than 8
electrons in their valence shell are said to have an _9_ octet.
When like atoms are joined by a covalent bond, the bonding
electrons are shared equally, and the bond is said to be __10__.
When the atoms in a bond are not the same, the sharing is uneven.
The degree of polarity of a bond between any two atoms is
determined by consulting a table of __11__ values.
If the electronegativity difference between the atoms is greater than
0.4 and less than 2, the bond is said to be __12__ . If it is greater
than 2, one atom wins the tug of war and the bond is said to be
__13__.
All molecules have __14__ forces between them. The attractions
between opposite poles of polar molecules constitute __15__. This
intermolecular attraction is one of several weak attractions between
molecules known collectively as __16__ forces. Another
intermolecular force is the __17__. Taken together, it is the
intermolecular forces that determine whether a covalent compound
will be a solid, liquid, or gas at room temperature.
1._____covalent________
2.______single_________
3.______double________
4.______triple__________
5.______coordinate______
6.______Lewis Structure__
7.______VSEPR________
8.______paramagnetic____
9.______expanded_______
10._____nonpolar_______
11.___electronegativity___
12._______polar________
13._______ionic________
14.____dispersion_______
15.____dipole forces_____
16.__Van der Waals_____
17.___hydrogen bond____
PART II. The following statements are not entirely true. Correct them.
_______1. A molecule with more than one possible Lewis Structure is said to undergo consonance.
They undergo resonance not consonance.
_______2. A molecule with polar bonds is always a polar molecule.
The molecule is only polar if one end is slightly positive and the other is slightly negative.
Sometimes the shape of the molecule causes the polar bonds to cancel each other out.
_______3. Covalently bound atoms always result in a neutrally charged compound.
They may also result in polyatomic ions.
_______4. The tendency of carbon to form four bonds to other atoms can be explained by the four p
electrons in its outer shell.
It can be explained by the process of orbital hybridization.
_______5. Unshared pairs of electrons on the outer atoms of molecules affect the 3D shape the most.
Those unshared pairs on the central atoms affect the 3D shape around that atom.
PART III. Problems.
1. Name the following binary molecular compounds (systematic or common names).
a) NO
__nitrogen monoxide__________
f) H2O2
_dihydrogen dioxide (hydrogen peroxide)__
b) PBr3
__phosphorus tribromide_______
g) SCl2
_sulfur dichloride_____________
c) CH4
__carbon tetrahydride__________
h) PF5
_sulfur pentafluoride___________
d) C4H8
__tetracarbon octahydride______
i) N2O3
_dinitrogen trioxide____________
e) I4O9
__tetraiodine nonoxide_________
j) O2
_oxygen_____________________
2. Write the formulas for the following compounds.
a) ammonia
___NH3____
f) dihydrogen monoxide
__H2O______
b) silicon tetrachloride
___SiCl4____
g) dichlorine heptoxide
__Cl2O7_____
c) selenium difluoride
___SeF2_____
h) boron trihydride
__BH3______
d) iodine gas
____I2______
i) dinitrogen octoxide
__N2O8_____
e) ozone
____O3_____
j) tetraiodine decoxide
__I4O10_____
3. Using Aufbau diagrams for each atom, indicate the sharing of electrons in covalent bond(s) between
oxygen and hydrogen in H2O.
4.
A) Draw Lewis Structures for the following molecules which obey the octet rule for each atom.
B) State the shape and bond angles around the central atom.
Formula
Lewis Structure
Shape
Bond Angles
pyramidal
107/
tetrahedral
109.5/
linear
180/
bent
105/
trigonal planar
120/
a) PBr3
b) CI4
c) SiO2
d) OBr2
e) CH2S
5.
A) Draw the Lewis Structure for the following exceptions to the octet rule.
B) State whether it is diamagnetic or paramagnetic.
C) If it is diamagnetic, state the shape and bond angles. (If it is paramagnetic, don’t do this part).
Formula
Lewis Structure
Di or Paramagnetic
Shape
Bond Angles
diamagnetic
trigonal planar
120/
paramagnetic
not responsible for
ignore!
diamagnetic
not responsible for
ignore!
a) BCl3
c) NO2
d) SCl6
6. For the following organic molecule,
a) Determine the number of sigma and pi bonds. ___13___ F __4___B
b) State the shape, bond angles, and type of hybridization around each central carbon atom (fill in chart).
shape
bond angles
hybridization
C1
trigonal planar
120/
sp2
C2
linear
180/
sp
C3
linear
180/
sp
C4
tetrahedral
109.5/
sp3
C5
trigonal planar
120/
sp2
C6
tetrahedral
109.5/
sp3
c) Calculate the bond dissociation energy for the entire molecule (table p339). Change Cl to H; S to O.
6(C-H) + 2(C=O) + 4(C-C) + 1(C C)
6(393 kJ/mol)+2(736 kJ/mol) + 4(347 kJ/mol) + 908 kJ/mol = 6126 kJ/mol
7. Draw the 3 possible resonant structures for NO3-.
8. A) Determine the type of bond that forms between the following elements (ionic, nonpolar covalent,
moderately polar covalent, very polar covalent). B) Draw the appropriate symbols for the bonds in the space
provided - indicate polar bonds with proper symbols; remember that ionic bonds result in ions). Table p 285.
Elements
Bond Type
S and F
very polar covalent
K and Cl
ionic
P and Se
nonpolar
Symbols
*+
S& F * -
K+ Cl*+
P& Se * -
8. Arrange the following in order of increasing ionic character (increasing difference).
K-Cl
N-H
Si-F
I-I
S-O
___I-I___, ___N-H___, ___S-O__, ___Si-F__, ___K-Cl__
9. Arrange the following intermolecular attractions in order of increasing strength:
dipole interactions, dispersion forces, hydrogen bonds
______dispersion forces_____, __dipole interactions_____, ____hydrogen bonds_____
10. Determine the types of intermolecular forces that exist between the following molecules (dispersion
forces, dipole forces, and/or hydrogen bonds). Hint: for some you have to determine whether or not they are
polar first. Just place a U (yes) or an X (no) in each box.
Molecule
Polar?
Dispersion Forces
Dipole Forces
Hydrogen Bonds
a) H-F
U
U
U
U
b) H2S
U
U
U
X
c) CS2
X
U
X
X
d) F-O-F
U
U
U
X
e) Br-Br
X
U
X
X
* Note: 10(d) H was changed to an F. I will not give you one like H-O-F on the test.