Question

What is the EAN (effective atomic number) of the underlined atom in the following complex?

$\left[\underset{–}{Cr}\right(en{)}_3{]}^{3+}$

Answer 1

The expression for the effective atomic number EAN is as given below.

$EAN=Z-X+Y$

Here, Z is the atomic number of metal,

X is the number of electrons lost during the formation of the metal ion from its atom and

Y is the number of electrons donated by the ligands.

For $\left[\underset{–}{Cr}\right(en{)}_3{]}^{3+}$,

$Z=24,X=3$ and $Y=3\times 4=12e^{-}$.

Hence, $EAN=24-3+12=33$.

Hence, the EAN of $\left[\underset{–}{Cr}\right(en{)}_3{]}^{3+}$ is 33.