Ethylenediaminetetraacetate (EDTA) ion is:

Solution & Explanation

\textbf{Answer:} (C) Hexadentate ligand with four “O” and two “N” donor atoms. \textbf{Solution:} Denticity is the number of donor atoms of a ligand that bind to the metal centre simultaneously. The ethylenediaminetetraacetate ion, $\mathrm{EDTA}{}^{4-}$, has six donor sites: two amine nitrogen atoms (from the ethylenediamine backbone) and four carboxylate oxygen atoms (one from each $-\mathrm{COO}-$ group). All six can coordinate to a single metal ion, wrapping around it and forming five chelate rings. EDTA is therefore a hexadentate chelating ligand with four O and two N donor atoms. Hence option (C) is correct.