Chemistry Reference
In-Depth Information
Because all compounds have overall charges of zero, we can deduce the
charges on some metals' cations from the total charge on the anions bonded to
them. For example, in CuCl and CuCl
2
, the charges on the copper ions are
and
1
2
,
respectively. The
1
charge on the copper ion in CuCl is required to
Cl
balance the
1
charge on one
ion. The
2
charge on the copper in CuCl
2
Cl
is required to balance the
1
charge on each of
two
ions.
EXAMPLE 5.10
What is the charge on each cation in (a) Cu
2
O and (b) CuO?
Solution
(a)
The charge on each cation must be
1
because two cations are required
O
2
to balance the charge on one
ion.
(b)
The charge on the cation must be
2
,
to balance the
2
charge on one
O
2
ion.
Practice Problem 5.10
What is the charge on each cation in (a) AgCl
and (b) PbO
2
?
Snapshot Review
❒
The charge on the formula of a complete compound must be zero, so
the total of the positive and of the negative charges must be equal.
The smallest integral numbers of cations and anions are used to
achieve charge neutrality.
ChemSkill Builder
3.2, 3.4
❒
Most main group cations and all monatomic anions have characteristic
charges that are easy to learn, so in their compounds with other ions,
the charges on the other ions are easy to deduce.
La
3
S
2
.
A. Write the formula for the compound of and
B. Write the formulas of the ions in each of the following compounds:
(a) VCl
2
(b) PbO
2
(c) Ti
2
O
3
.
5.5
Covalent Bonding
Metal atoms can donate electrons to nonmetal atoms, but nonmetal atoms do
not form monatomic positive ions because they would have to donate too many
valence electrons to form octets. (Single nonmetal atoms do not donate elec-
trons at all, but some groups of nonmetal atoms can. This will be discussed later
in this section.)
Nonmetal atoms can accept electrons from metal atoms if such atoms are
present; otherwise, they can attain an octet by
electron sharing.
A
covalent
bond
consists of shared electrons. One pair of electrons shared between two
atoms constitutes a
single
covalent bond, generally referred to as a
single bond.
An
unshared pair
of valence electrons is called a
lone pair.
Elements or com-
pounds bonded only by covalent bonds form molecules.
The formula unit of a covalently
bonded group of atoms is called
a molecule.
