Question

Select the coloured compound amongst the following:

(Atomic no. $Ti=22,Cr=24,Cu=29,Zn=30$)

• A. $TiC{l}_4$
• B. $CrC{l}_3$
• C. $ZnC{l}_2$
• D. $CuCl$

Answer 1

Answer: (B)

$CrC{l}_3$

TiCl${}_4$

Electronic configuration of Ti is $\left[Ar\right]3d^{2}4s^2$.

For Ti${}^{4+}$ - $\left[Ar\right]3d^{0}4s^0$

Since no electron is present, so it is colourless.

CrCl${}_3$

Electronic configuration of Cr is $\left[Ar\right]3d^{5}4s^1$

For Cr${}^{3+}$ - $\left[Ar\right]3d^{3}4s^0$.

Since there is a presence of d-electrons, so it is coloured. There is partially filled d-orbital so due to d-d transition colour is imparted to this compound.

ZnCl${}_2$

Electronic configuration of Zn - $\left[Ar\right]3d^{10}4s^2$

For Zn${}^{2+}$ - $\left[Ar\right]3d^{10}4s^0$

Because of fully filled d orbital, the compound is colourless.

CuCl

Electronic configuration of Cu${}^{+}$ is $3d^{10}4s^0$

Due to fully filled d-orbital, it is colourless.