Question

What term is used to describe the number of nearest neighbors?

Answer 1

Coordination number:

• “The coordination number (C.N.) of a metal ion in a complex can be defined as the number of ligand donor atoms to which the metal is directly bonded.”
• For example, in${\left[{\mathrm{PtCl}}_6\right]}^{2+}$, the coordination number is$6$.

Nearest neighbors:

• In a coordination complex, the nearest neighbors to the central metal are ligands.
• The number of ligands or the nearest neighbors is given by the term ‘coordination number’.
• For example, In $\mathrm{Ni}{\left(\mathrm{CO}\right)}_4$​, four carbonyl ligands are bonded to $\mathrm{Ni}$ atom. Hence, the coordination number of $\mathrm{Ni}$ in $\mathrm{Ni}{\left(\mathrm{CO}\right)}_4$​ is four. Thus, carbonyls are nearest neighbors of Nickel metal atom.