Coordination Number and Geometry

For transition metal complexes, the coordination number determines the geometry around the central metal ion. Table 1 compares coordination numbers to molecular geometry. The most common structures of the complexes in coordination compounds are octahedral, tetrahedral, and square planar.

Many transition metals exhibit multiple oxidation numbers contributing to their unique properties, such as colors. But how is the metal’s oxidation number determined?

Coordination compounds are electrically neutral species consisting of a coordination complex and counterions with a primary and secondary valence.

The primary valence...