Question

The coordination number and the oxidation state of the element $E$' in the complex $\left[E\right(en{)}_2\left(C_2{O}_4\right)]N{O}_2$ (where (en) is ethylene diamine) are respectively:

• A. 4 and 3
• B. 6 and 3
• C. 6 and 2
• D. 4 and 2

Answer 1

The correct option is B 6 and 3

The coordination number is the number of coordinate covalent bonds formed with central metal atom. ligand en is a bidentate ligand that is it has two donor atoms in one molecule. So, when two en ligands will attach to central atom they will make four covalent coordinate bonds. Also, Oxalate $\left(C_2{O}_4\right)$ is bidentate ligand making two coordinate covalent bonds at a time. Hence overall the coordination number of the element E is $4+2=6$.

The oxidation number can be calculated by adding the charges of all the ligands and counter ions (ions present outside the central atom).

Let the oxidation state of element E be $x$.

Ligand en is neutral. Oxalate carries$-2$charge $N{O}_2$ (counter ion) carries $-1$charge.

So, $x+(2\times 0)+(-2)+(-1)=0$

$x-2-1=0$

$x=+3$

Hence,option B is correct.