Chemistry - Coordination Chemistry Question with Solution | TestHub

${\mathrm{EDTA}}^{4-}$  is a hexadentate ligand containing four negative charges on its corner oxygen atoms as follows :

Being a hexadentate ligand, it forms a ring like structure through chelation.

The central metal ion $\mathrm{Co}$ is in the centre, coordinated to the two $\mathrm{N}$ atoms and the four ${\mathrm{O}}^{-}$ ions through chelation. Now, if we observe, we see that each $\mathrm{N}$ atom forms four $\mathrm{N} - \mathrm{Co} - \mathrm{O}$ bonds with the four ${\mathrm{O}}^{-}$ ions. Therefore, two $\mathrm{N}$ atoms will form $2 \times 4 = 8$  $\mathrm{N} - \mathrm{Co} - \mathrm{O}$ bonds in the complex structure of $\left[\mathrm{Co}\right(\mathrm{EDTA}){]}^{1-}$. Each bond will have a certain bond angle. Hence, it can be concluded that the total number of $\mathrm{N} - \mathrm{Co} - \mathrm{O}$ bond angles in the complex ion is $8$.