Name:__[KEY]____________________
Date:___________
Period:____
Review Chemistry I Unit 6: Covalent Bonding and Nomenclature
1. Why do atoms share electrons in covalent bonds with other atoms rather than
remaining as single atoms?
Atoms form covalent bonds to obtain more stable electron arrangements.
2. A molecule is a neutral group of atoms held together by ______ .
A.
B.
C.
D.
ionic bonds
unshared electrons
partial charges
covalent bonds
3. Compounds formed by covalent bonds usually contain _______________.
A.
B.
C.
D.
halogens and oxygen
two or more nonmetals
a metal and a nonmetal
positive and negative ions
4. Which of the following is a molecular compound?
A.
B.
C.
D.
Na2O
AlCl3
SCl6
CuO
5. How do atoms form covalent double bonds?
A.
B.
C.
D.
C
C
One atom loses two electrons to the other atom in the bond.
Two atoms share two pairs of electrons.
Two atoms share two single electrons.
Two atoms share one electron.
6. Which of these elements does NOT exist as a diatomic molecule?
A.
B.
C.
D.
P
Cl
O
N
?
?
1
7. A bond formed between a carbon atom and hydrogen atom is likely to be ____.
A.
B.
C.
D.
polar covalent
dipolar
ionic
nonpolar covalent
8. Which of the following bonds is the most polar (i.e. has the greatest difference in electronegativity)?
A.
B.
C.
D.
C—C
H—N
O—H
H—Cl
9. Which of the following covalent bonds is the least polar?
A.
B.
C.
D.
H—Cl
H—C
Cl—Cl
H—N
10. Which is TRUE of a nonpolar covalent bond?
A.
B.
C.
D.
electrons are shared unequally between atoms
a cation is bonded to an anion
electrons are transferred between atoms
electrons are shared equally between atoms
11. Draw the Lewis dot structure for CO2 in the box:
Does CO2 contain polar bonds? _Yes_
If so, how many? _2__
Is CO2 a polar molecule? No
If not, explain why not. The polar bonds are
arranged symmetrically and cancel out.
12. The following molecules contain polar bonds. Which is the only nonpolar molecule?
A. HCl
B. NH3
C. H2O
D. CBr4
(hint: drawing the Lewis structures can help)
2
water molecule
water molecule
13. Water molecules are polar because they have polar bonds (due to different electronegativities)
that are arranged asymmetrically (do not cancel out).
14. Describe properties that are common in typical molecular compounds.
conductor:
good or poor
melting point: high
or
low
boiling point: high
or
low
net charge:
neutral or charged
#15-20 Write the NAME or FORMULA for the following molecular compounds:
15. CS2
carbon disulfide
16. CCI4
carbon tetrachloride
17. S2O6
disulfur hexoxide
18. triboron monoxide
B3O
19. tetraphosphorus pentoxide
P4O5
20. arsenic trihydride
AsH3
21. In drawing a Lewis structure, what is special about hydrogen (H) ?
A.
B.
C.
D.
It achieves an octet of 8 electrons.
It can form up to four bonds with 8 shared electrons.
It can only form one double bond.
It can only form one single bond with no unshared electrons around it.
3
For #22-27,
-Draw the Lewis dot structures for the following compounds.
-List how many unshared pairs of electrons are in the molecule.
-Identify the molecule as polar or nonpolar by circling the correct label.
22. HBr
unshared pairs: _3_
polar or nonpolar
23. NI3
unshared pairs: _10_
polar or nonpolar
24. N2
unshared pairs: _2_
polar or nonpolar
25. Cl2
unshared pairs: _6_
polar or nonpolar
26. SO2
unshared pairs: _6_
polar or nonpolar
27. CH2F2
unshared pairs: _6_
polar or nonpolar
4