Question

The total number of coordination sites in $EDTA^{3-}$ is _____________.

Answer 1

6

Answer 2

The species $EDTA^{3-}$ is actually $HEDTA^{3-}$, which has two nitrogen atoms and three deprotonated carboxylate groups ($COO^-$), totaling 5 donor atoms. The remaining carboxylic acid group ($COOH$) has a carbonyl oxygen that can also coordinate. Thus, the total number of coordination sites is $2 (\text{N}) + 3 (\text{O from } COO^-) + 1 (\text{O from } COOH) = 6$.