The coordination number in coordination compounds refers to the number of ligands atoms, ions, or molecules that are directly bonded to the central metal atom or ion. The coordination number plays a significant role in determining the isomerism of coordination compounds. Isomerism is the phenomenon in which two or more compounds have the same molecular formula but different structural arrangements.There are two main types of isomerism in coordination compounds: structural isomerism and stereoisomerism.1. Structural Isomerism: This type of isomerism arises due to the differences in the connectivity or arrangement of atoms in the coordination compounds. Coordination number influences structural isomerism in the following ways:a Linkage Isomerism: This occurs when the coordination number remains the same, but the ligand binds to the central metal atom/ion through different donor atoms. For example, the thiocyanate ion SCN- can bind to a metal ion through the sulfur atom S or the nitrogen atom N , leading to linkage isomers.b Coordination Isomerism: This occurs in coordination compounds containing complex cations and anions. The coordination number affects the distribution of ligands between the cationic and anionic complexes. For example, [Co NH3 6][Cr CN 6] and [Cr NH3 6][Co CN 6] are coordination isomers.2. Stereoisomerism: This type of isomerism arises due to the differences in the spatial arrangement of ligands around the central metal atom/ion. Coordination number influences stereoisomerism in the following ways:a Geometrical Isomerism: This occurs when the coordination number and the ligands remain the same, but their spatial arrangement around the central metal atom/ion is different. Geometrical isomerism is common in coordination compounds with coordination numbers 4 square planar and tetrahedral geometries and 6 octahedral geometry . For example, in the square planar complex [Pt NH3 2Cl2], the two possible geometrical isomers are cis with two Cl atoms adjacent to each other and trans with two Cl atoms opposite each other .b Optical Isomerism: This occurs when the coordination compounds are non-superimposable mirror images of each other, known as enantiomers. Optical isomerism is common in coordination compounds with coordination numbers 4 tetrahedral geometry and 6 octahedral geometry . For example, in the octahedral complex [Co en 3]3+ where en = ethylenediamine , the two enantiomers are non-superimposable mirror images and exhibit optical isomerism.In conclusion, the coordination number significantly affects the isomerism in coordination compounds by influencing the connectivity and spatial arrangement of ligands around the central metal atom/ion. Different coordination numbers lead to various types of structural and stereoisomerism, resulting in diverse chemical and physical properties for the coordination compounds.