Isomers are two or more compounds that have the same chemical formula but a different arrangement of atoms. Because of the different arrangement of atoms, they differ in one or more physical or chemical properties. Two principal types of isomerism are known among coordination compounds. Each of which can be further subdivided.

(a) Stereoisomerism

(i) Geometrical isomerism (ii) Optical isomerism

(b) Structural isomerism

(i) Linkage isomerism

(ii) Coordination isomerism

(iii) Ionisation isomerism

(iv) Solvate isomerism

Stereoisomers have the same chemical formula and chemical bonds, but they have different spatial arrangement. Structural isomers have different bonds.

[Cr(en)₃]³⁺ shows which type of isomerism?

Optical isomerism

[Cr(en)₃]³⁺ shows optical isomerism.

Octahedral complexes having formula M(A-A)3 shows optical isomerism.