You may
use a periodic table and a calculator to do this test.
Multiple-choice section
Please write the letter of the most correct
answer in the space next to the problem for each of the following ten problems:
1) How
many valence electrons does gallium have?
a) 1 c) 5
b) 3 d) 13
2) How
many electrons does phosphorus have to gain in order to achieve a noble-gas
electron configuration?
a) 2 c) 5
b) 3 d) 4
3) How
many valence electrons are transferred from the nitrogen atom to each potassium in the formation of the
compound potassium nitride?
a) 0 c) 3
b) 1 d) 5
4) Which
of the following takes place in an ionic bond?
a) Two atoms share two electrons
b) Two atoms share electrons such that both
follow the octet rule.
c) Like-charged ions attract
d) Oppositely-charged ions attract
5) What
is the net charge of the ionic compound calcium fluoride?
a) -2 c) +2
b) 0 d) -1
6) Ionic
compounds are normally found in what state at room temperature?
a) solid c) gas
b) liquid d) none of these
7) The
melting temperature of potassium chloride is relatively…
a) low c) KCl does not melt
b) high d) about room temperature
8) What
does the term “coordination number” refer to?
a) The number of oppositely charged ions
surrounding a particular ion
b) The number of atoms in a unit cell
c) The number of valence electrons in an
atom
d) The number of times a compound forms
covalent bonds
9) What
characteristic of metals makes them good electrical conductors?
a) Mobile valence electrons
b) Mobile protons
c) Their crystal structures rearrange
easily
d) Mobile cations
10) How many electrons are shared between two atoms in a double
covalent bond?
a) 8 c) 4
b) 6 d) 2
11) How many unshared pairs of electrons are there in hydrogen
iodide?
a) 1 c) 3
b) 6 d) none of these
12) Which of the following elements occurs naturally as a diatomic
molecule with three covalent bonds?
a) oxygen c) fluorine
b) hydrogen d) nitrogen
13) When one atom contributes both bonding electrons in a single
covalent bond, the bond is called a(n)…
a) ionic covalent bond
b) polar covalent bond
c) one-sided covalent bond
d) coordinate covalent bond
14) Which of the following pairs of elements can be joined by a
covalent bond?
a) Li and Br c) Mg
and C
b) N and C d) He and O
15) In which of the following compounds/ions is there an exception
to the octet rule?
a) SF6 c) MgO
b) PH3 d) BH4+1
Answer Key:
1) b
– Valence electrons are the number of s- and p-electrons since the last noble
gas. The d-electrons don’t count.
2) b
– It has five valence electrons, and wants eight like argon.
3) a
– Electrons are transferred from K to N, not the other way around.
4) d
5) b
– Ionic compounds have no overall charge, because the cations and anions cancel
each other out.
6) a
– Ionic compounds generally have high melting and boiling points because the
positive and negative charges are tightly bound to one another.
7) b
– See explanation above
8) a
9) a
– If this doesn’t make sense, study the “electron sea theory” of metallic
bonding.
10) c – Because each bond contains two electrons, a double bond
will contain 4 electrons.
11) c – All three unshared electron pairs are on the iodine atom.
12) d – The others are all naturally diatomic, but only N2
has triple bonds.
13) d
14) b – The differences in electronegativity between the other elements
are too large for covalent bonding to occur.
15) a – Sulfur has six electron pairs around it.
