NAMES AND FORMULAS OF COMPOUNDS
This handout describes the systems that are used for ionic compounds and for binary
Also included is a list of several compounds which are known by
****** IONIC COMPOUNDS ******
The name of an ionic compound is the name of the cation followed by the name of
The charges of the ions need to be considered, since the compound as a whole
must be neutral.
Constant charge monatomic cations
For our purposes, all metal elements in Groups 1(1A), 2(2A), and 13(3A) are
assumed to form cations of charges 1+, 2+ and 3+, respectively.
In addition, Ag and Zn are
assumed to be constant charge ions, forming Ag
All ions in this
category are named simply by the name of the element.
lithium ion, Li
magnesium ion, Mg
aluminum ion, Al
potassium ion, ________
gallium (Ga) ion, ________
Variable charge monatomic cations
Many metal elements can form cations of different charges depending on the
These charges are therefore not predictable unless some other information,
such as the formula, is provided.
For our purposes, the elements in this category include all
metal elements other than the constant charge cases (above).
Ions in this category are
named with the actual charge specified; in written names, the charge is given by Roman
numerals in parentheses.
chromium(II) ion, Cr
chromium(III) ion, Cr
manganese(II) ion, Mn
manganese(III) ion, Mn
manganese(IV) ion, Mn
tin(II) ion, ________
tin(IV) ion, ________
gold(I) ion, ________
gold(III) ion, ________
Constant charge monatomic anions
The common anions formed by the nonmetals and the metalloids are of a charge
equal to the quantity [Group number – 18] or [Group number – 8] in the A/B system.
name of the ion is the root of the element name, then
nitride ion, N
oxide ion, O
chloride ion, Cl
phosphide ion, ________
iodide ion, ________