http://www.ck12.org Chapter 7. Chemical Nomenclature
2.
Step 3: Think about your result.
The formula for barium chloride is BaCl 2. Notice that the charge of the chloride ion needs to be written as 1−
rather than just –in order to do the crisscross. However, the number 1 is not used as a subscript. The formula for
chromium(III) oxide is Cr 2 O 3.
Practice Problems- Write formulas for the binary ionic compounds formed by the following pairs of elements:
a. cesium and fluorine
b. calcium and sulfur
c. aluminum and chlorine
d. zinc and nitrogen - Write the formula and give the name for the compound formed by each of the following ion pairs:
a. Fe^3 +and O^2 −
b. Ni^2 +and S^2 −
c. Au+and Cl−
d. Sn^4 +and I− - Give names for the following compounds:
a. Ag 2 S
b. PdO
c. PtCl 4
d. V 2 O 5
Ternary Ionic Compounds
Not all ionic compounds are composed of only monatomic ions. Aternary ionic compoundis an ionic compound
composed of three or more elements. In a typical ternary ionic compound, there is still just one type of cation and
one type of anion, but the cation or the anion (or sometimes both) is a polyatomic ion.
Polyatomic Ions
Apolyatomic ionis an ion composed of more than one atom. The ammonium ion consists of one nitrogen atom and
four hydrogen atoms. Together, they comprise a single ion with a 1+ charge and a formula of NH 4 +. The carbonate