Question

The complex ion having minimum wavelength of absorption in the visible region is

• A. $\left[ Co \left( NH _3\right)_6\right]^{3+}$
• B. $\left[ CoCl \left( NH _3\right)_5\right]^{2+}$
• C. C is $-\left[ CoCl _2\left( NH _3\right)_4\right]^{+}$
• D. Trans $-\left[ CoCl _2\left( NH _3\right)_4\right]^{+}$

Answer 1

Answer: (A)

Here $\left[ Co \left( NH _3\right)_6\right]^{3+}$ have minimum wavelength of absorption in the visible region as for it splitting energy is more as it has all strong ligands. $\Delta_0$ (splitting energy) $\propto \frac{1}{\lambda(\text { Absorbed })}$ Basic strength of ligand $C > N > O > X$ (halogen) donor.