Barrons SAT Subject Test Chemistry, 13th Edition

Li +, N3−

Li 3 N

Lithium nitride

*Ionic charges are shown as numerical exponents followed by the charge.

Category II—Binary Ionic Compounds

In category II binary ionic compounds, the metals form more than one ion, each
with a different charge. The metallic ions (cation) ionically bind with a negatively
charged ion (anion).
The following chart lists many of the metals that form more than one type of
ionic cation and therefore more than one binary ionic compound with a given
anion.

Common Category II Cations (Multivalent Metals)

*This form of mercury(I) ions always occurs bonded together as a Hg 2 2+ ion.
Although the following metals are “transition” metals, they form only one
type of cation. So a Roman numeral is not used when naming their compounds.

Ag1+

Silver

Cd2+

Cadmium

Zn2+

Zinc

Example

The compound containing the Fe2+ ion and the compound containing the Fe3+ ion
both combine with the chloride ion to form two different compounds. Using the
crisscross system, you get the formula FeCl 2 for iron(II) chloride.