Nomenclature I
Binary Compounds of Active Metals and Active Non-Metals
If you are not familiar with the Periodic Table,
have a look at the inside front cover of OFB.
Many ionic compounds are formed by the combination of active metals (the
alkali metals of Group 1, the alkaline earth metals of Group 2, and aluminum
(Group 13)) with active non-metals (the halogens of Group 17, oxygen and
sulfur (Group 16), and nitrogen and phosphorus (Group 15)). In compounds
such as potassium iodide (KI), calcium oxide (CaO), and aluminum nitride
(AlN), the metal atom has lost a number of electrons equal to its group
number and the non-metal has gained a number of electrons equal to
eighteen minus its group number). Thus, potassium iodide contains equal
numbers of K+ and I– ions; calcium oxide contains equal numbers of Ca2+
and O2– ions; and aluminum nitride contains equal numbers of Al3+ and N3–
ions.
Of course, there is no reason that an ionic compound must contain equal
numbers of cations and anions. Potassium oxide (K2O) contains two K+ ions
for every O2– ion. Likewise, calcium iodide (CaI2) contains two I– ions for
every Ca2+ ion. The formulas of these compounds, and all ionic compounds,
are determined by the rule of electroneutrality (the total number of positive
charges must equal the total number of negative charges).
In binary compounds with active metals, hydrogen acquires a charge of +1.
Thus, rubidium hydride has the formula, RbH, and magnesium hydride has
the formula, CaH2.
The names of binary ionic compounds follow the pattern:
(name of element in cation) (root of name of element in anion) ide
Thus, cesium bromide is CsBr and AlCl3 is aluminum chloride. Likewise,
the formula for strontium fluoride is SrF2 and formula for aluminum sulfide
is Al2S3.
Exercises
1. Name the compounds identified below:
a. NaCl
b. KBr
c. MgF2
d. CaCl2
e. CaS
f. SrI2
g. RbF
h. BaH2
i. AlH3
j. Li2O
k. BaCl2
l. BaS
m. CsCl
n. RbBr
o. BeF2
p. CaF2
q. CaSe
r. SrS
s. BaI2
t. RaH2
u. AlF3
v. Li2S
w. Li3N
x. AlP
2. Give the correct formula for each compound named below.
a.
b.
c.
d.
e.
f.
g.
h.
i.
sodium fluoride
potassium chloride
calcium sulfide
barium bromide
strontium oxide
aluminum bromide
aluminum oxide
lithium sulfide
rubidium sulfide
j. calcium hydride
k. magnesium oxide
l. strontium nitride
m. lithium hydride
n. radium sulfide