Chemistry Reference
In-Depth Information
1
1
Figure 6.2
Cations with
Constant Charges and Cations
with Varying Charges
A
l
k
a
l
i
A
l
k
a
l
i
n
e
E
a
r
t
h
s
Constant
Constant
Al
Sc
Y
La
Zn
Cd
Ag
M
e
t
a
l
s
Variable
Ac
Mostly 3
EXAMPLE 6.5
Co
2
Co
3
.
Name
and
Solution
Cobalt(II) ion and cobalt(III) ion, respectively.
EXAMPLE 6.6
How can we tell whether the chromium ion in the compound
CrCl
2
has a
2
or
3
charge?
Solution
We know that the chloride ion has a charge; the chromium ion must have
a charge to balance the charge on two chloride ions and make the com-
pound neutral. (See Section 5.4.)
1
2
(NH
4
)
3
VO
4
?
Practice Problem 6.6
What is the charge on the anion in
In writing formulas for ionic compounds from their names, we must remem-
ber the rules from Chapter 5. Be sure to balance the number of positive and
negative charges! The charges on the cations are implied for some cations (the
constant type) and stated explicitly in the name for the others. The charge on a
monatomic anion is equal to the group number minus 8 (see Section 5.2).
EXAMPLE 6.7
Write the formula for each of the following compounds:
(a) Magnesium sulfide
(b) Sodium iodide
(c) Lead(IV) oxide
(d) Aluminum oxide
