Introduction

• are two or more molecules or ions that contain the same number and kinds of atoms, but the atoms are arranged differently (i.e., the structures are non-superimposable).
• have the same molecular formula.
• have different physical and/or chemical properties.
• do not exist for all coordination compounds.

Structural isomers: contain the same number and kinds of atoms, but one or more bonds is/are different (i.e., the connectivity between atoms is different). There are two types of structural isomers:

• coordination isomers, and
• linkage isomers.

Stereoisomers: contain the same number and kinds of atoms, and the same number and kinds of bonds (i.e., the connectivity between atoms is the same), but the atoms are arranged differently in space. There are two types of stereoisomers:

• geometric isomers, and
• optical isomers.

Note that coordination isomers and linkage isomers can exist only with coordination compounds. Geometric isomers and optical isomers occur not only with coordination compounds but also with many organic compounds.