Question

Which has maximum EAN of the underlined atoms?
$(Cr=24,Co=27,Fe=26,Ni=28)$

• A. $\left[\underset{–}{Cr}\right(EDTA){]}^{-}$
• B. $\left[\underset{–}{Co}\right(en{)}_3{]}^{3+}$
• C. $\left[\underset{–}{Fe}\right(C_2{O}_4{)}_3{]}^{3-}$
• D. $\left[\underset{–}{Ni}\right(CN{)}_4{]}^{2-}$

Answer 1

The correct option is B $\left[\underset{–}{Co}\right(en{)}_3{]}^{3+}$

$EAN=$ [atomic number of metal] $-$ [number of electrons lost in formation of its ion]
$+$ [number of electrons gained from ligand]
The EAN is maximum for $\left[Co\right(en{)}_3{]}^{3+}$
(A) $\left[Cr\right(EDTA){]}^{-}$ has EAN $=24-3+12=33$.
(B) $\left[Co\right(en{)}_3{]}^{3+}$ has EAN $=27-3+12=36$.
(C) $\left[Fe\right(C_2{O}_4{)}_3{]}^{3-}$ has EAN $=26-3+12=35$.
(D) $\left[Ni\right(CN{)}_4{]}^{2-}$ has EAN $=28-2+8=34$.