Explain the classification of ligands on the basis of their denticity.

(N/A) The total number of donor atoms in a ligand is called its denticity.
$(i)$ Monodentate ligands: These ligands have only one donor atom or are coordinated through a single electron pair with a metal ion. They are also known as unidentate ligands. They may be neutral or anionic.
Example:
$(a)$ Neutral: $H_{2}O, CO, NH_{3}, C_{6}H_{5}N$ (pyridine) etc.
$(b)$ Anionic: $Cl^{-}, Br^{-}, I^{-}, NO_{2}^{-}, SCN^{-}$ etc.
$(ii)$ Polydentate ligands: These ligands may be bidentate,tridentate,tetradentate,pentadentate,and hexadentate if the number of donor atoms are $2, 3, 4, 5$ and $6$ respectively.
Examples:
$C_{2}O_{4}^{2-}$ (bidentate),$PO_{4}^{3-}$ (tridentate),$N(CH_{2}CH_{2}NH_{2})_{3}$ (tetradentate),ethylene diamine triacetate ion (pentadentate),and ethylene diamine tetraacetate ion (hexadentate).