Question

Identify the correct increasing order of crystal field stabilization energy value for the given complexes.

• A. ${\left[Ir{\left(N{H}_3\right)}_6\right]}^{3+}<{\left[Rh{\left(N{H}_3\right)}_6\right]}^{3+}<{\left[Co{\left(N{H}_3\right)}_6\right]}^{3+}$
• B. ${\left[Rh{\left(N{H}_3\right)}_6\right]}^{3+}<{\left[Co{\left(N{H}_3\right)}_6\right]}^{3+}<{\left[Ir{\left(N{H}_3\right)}_6\right]}^{3+}$
• C. ${\left[Co{\left(N{H}_3\right)}_6\right]}^{3+}<{\left[Ir{\left(N{H}_3\right)}_6\right]}^{3+}<{\left[Rh{\left(N{H}_3\right)}_6\right]}^{3+}$
• D. ${\left[Co{\left(N{H}_3\right)}_6\right]}^{3+}<{\left[Rh{\left(N{H}_3\right)}_6\right]}^{3+}<{\left[Ir{\left(N{H}_3\right)}_6\right]}^{3+}$

Answer 1

Answer: (D)

The elements in the $2^{nd}$ and $3^{rd}$ transition series (the $4d$ and $5d$ elements) have large splitting than those in $3d$ series. So, the order of $CFSE$ is
$[Co(N{H}_3{)}_6{]}^{3+}<[Rh(N{H}_3{)}_6{]}^{3+}<[Ir(N{H}_3{)}_6{]}^{3+}$