Question

Which among the following is colorless?

• A. ${\mathrm{Sc}}^{2+}$
• B. ${\mathrm{Zn}}^{2+}$
• C. ${\mathrm{Ti}}^{3+}$
• D. ${\mathrm{V}}^{3+}$

Answer 1

The correct option is B

${\mathrm{Zn}}^{2+}$

Explanation for the options

(B)${\mathrm{Zn}}^{2+}$

• The electronic configuration of ${\mathrm{Zn}}^{2+}$ is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}3{\mathrm{d}}^{10}$.
• ${\mathrm{Zn}}^{2+}$is colorless due to the absence of unpaired electrons.
• It has completely filled d-orbitals

Explanation for incorrect options

• The electronic configuration of ${\mathrm{Sc}}^{2+}$ is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}3{\mathrm{d}}^1$.So, one unpaired electron is present in the d orbital.
• The electronic configuration of ${\mathrm{Ti}}^{3+}$ is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}3{\mathrm{d}}^1$.So, one unpaired electron is present in the d orbital.
• The electronic configuration of ${\mathrm{V}}^{3+}$ is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}3{\mathrm{d}}^2$.So, two unpaired electrons are present in the d orbital.
• Due to unpaired electrons in ${\mathrm{Sc}}^{2+}$,${\mathrm{Ti}}^{3+}$, and ${\mathrm{V}}^{3+}$, these are colored.
• Hence, options (A), (C), and (D) are incorrect.

Hence, option (B) is correct. ${\mathrm{Zn}}^{2+}$ is colorless.