PRACTICE TEST: BONDING
NAME:
DR. B
The test will cover everything we have worked on for the past three weeks. This practice test
covers some of the types of questions you may see on the test. Use your notes, book,
worksheets, labs, and warm-ups to prepare for the exam. Also look at presentations and links at
www.breslyn.org.
1. Draw the electron dot structures for:
O2
N
H2S
CF4
Br2
Search internet on “Lewis structure for O2, N, etc.
2. Describe the periodic trend for electronegativity. Which has a greater difference in electronegativity
and is more polar, H2O or H2S? Which would form stronger hydrogen bonds?
As we move across periods (to the right) electronegativity increases. Fluorine is the most
electronegative.
As we move down groups, electronegativity decreases. Francium is the least electronegative.
H2O is more polar because there is a larger electronegativity difference between H and O than
there is between H and S. The larger the electronegativity difference, the more polar the
molecule will be (remember: covalent is two non-metals bonding).
H2O would form stronger hydrogen bonds because the difference in electronegativity between H
and O results in H being slightly positive and O being slightly negative. Therefore the opposite
charges on different water molecules would attract each other forming hydrogen bonds (link to
animation).
3. Describe the properties of ionic, covalent, and metallic bonds. Give examples of each.
See page 244 in your book for a table comparing ionic and covalent (molecular) compounds)
Wikipedia has a short article on metallic bonds (link) that is helpful.
4. Label the following compounds as metallic, ionic, polar covalent, or non-polar covalent.
H2O (polar covalent)
KCl (ionic)
Cl2 (nonpolar covalent)
CaSO4 (ionic)
CH4 (nonpolar covalent)
Fe (metallic)
5. What type of bonds do the following compounds have?
PCl3 (polar covalent),
CH 4 (nonpolar covalent),
FeCl3 (ionic), BeF2 (ionic),
Cl2 (nonpolar covalent),
NH3 (polar covalent – draw the dot structure to see how the nonbonding electrons make it asymmetrical.) ,
HCl (polar covalent),
CuSO 4 (ionic)
6. Describe why atoms form chemical bonds.
 Because of attractions between atoms.
 To gain a full outer shell of electrons (obtaining an octet).
 To become more stable (by losing energy).
7. Why are valence electrons important in chemistry? How does this relate to ionic, covalent,
and metallic bonds?
Valence electrons are involved in chemical bonding. This is because they are on the outside of
the electron and are the first electrons to come in contact with other atoms.
In ionic compounds they are transferred (gained or lost) between atoms. This is due to the large
difference in electronegativity between atoms.
In covalent (molecular) bonds they are shared. Here the electronegativity difference is smaller
and sharing is possible. If they are shared unequally it is called a polar covalent bond.
8.
Name three atoms from two different groups that will form an ionic bond with Br.
Mg will bond with Br to form MgBr2
Na will bond with Br to form NaBr
H will bond with Br to form HBr
9. How many electrons are in a single, double, and triple bond?
Single = 2, Double = 4, Triple = 6
10. Which bond is most polar and why? Which is non-polar?
HCl,
HBr,
HS,
HC,
F2
MOST  HCl
HBr
HS
HC
F2
 LEAST
(F2 is nonpolar)
11. When an atom of magnesium loses two electrons, what is the charge on the resulting ion?
Write the electron configuration for ion? What can you say about the configuration?
When an atom of magnesium loses two electrons is has a charge of +2, written Mg 2+.
1s22s22p6
The configuration represents a full outer shell (an octet). It has the same configuration as the
nobel gas Ne.
12. What does VSEPR Theory tell us?
That the electron clouds around the atoms in a molecule will repel each other and spread out,
moving as far away from each other as possible. This what gives atoms distinct shapes.
Check this website (link) for more examples and information.
13. What is the shape of CH4? - tetrahedral
Of H2O? - bent
Of NH3? - pyramidal
Of Cl2? - linear
14. Label the functional groups below (alkane, alkene, alkyne, alcohol, amine, carboxylic acid)
amine
alkane
alcohol
alkene
alkyne
* R stands for the “rest of the molecule” which is not shown.
carboxylic
acid