Question

What is a coordination site?

Answer 1

In complexes, there are ions, molecules or atoms which are bonded to the central metal ion. In crystals, each ion is surrounded by a specific number of ions of opposite charge.

Complete step-by-step answer: - Coordination number is also known as ligancy. This term is mainly used in crystallography and materials science.
- Coordination number is the number of atoms, molecules or ions bonded to a central metal atom. The ions, molecules or atoms surrounding the central metal atom is called ligands. This is in the case of complexes.
- In complexes formed by d-block transition metals, the most common coordination number is 6 and the structure is octahedral. Metals of f-block can have higher oxidation numbers because of their greater ionic radii and availability of more orbitals for bonding. They have a coordination number varying between 8 to 12.
- In case of crystals, the coordination number is the number of ions that is present in the immediate surroundings of an ion of opposite charge in a crystal lattice. For example, sodium chloride has a face centered cubic lattice. Each sodium ion is surrounded by six chloride ions and each ion is surrounded by six sodium ions. So, the coordination number for sodium chloride is 6.
- Thus, coordination number is the number of ions, atoms or molecules bonded to a central atom in coordination chemistry. In crystallography, it is the number of ions in immediate surroundings of an ion.

Note: Coordination compounds are formed by complete transfer of electrons from a single metal atom which is beyond its normal valency. But double salts are formed from normal valency.