Question

Which of the following compounds is/are expected to be colored?

• A. $Ti(N{O}_3{)}_4$
• B. $\left[Cu\right(NCC{H}_3{)}_4]B{F}_4^{-}$
• C. $\left[Cr\right(N{H}_3{)}_6{]}^{3+}+3C{l}^{-}$
• D. $K_3\left[V{F}_6\right]$

Answer 1

Answer: (C), (D)

The correct options are
C $\left[Cr\right(N{H}_3{)}_6{]}^{3+}+3C{l}^{-}$
D $K_3\left[V{F}_6\right]$

(A) ${}_{22}T{i}^{4+}=3d^{o}4s^o$. No unpaired electrons, therefore it is colourless.

(B) ${}_{29}C{u}^{+}=3d^{10}4s^o$. No unpaired electrons, therefore it is colourless.

(C) ${}_{24}C{r}^{3+}=3d^{3}4s^o$. In the complex $\left[Cr\right(NH3{)}_6{]}^{3+}$, the chromium(III) ion has the outer electronic configuration $3d^3$. Thus, it contains three unpaired electrons and is violet in color.

(D) ${}_{23}{V}^{3+}=3d^{2}4s^o$. In the complex $K_3\left[V{F}_6\right]$, the vanadium(III) ion has outer electronic configuration $3d^2$. Thus, it contains two unpaired electrons and is green in color.