Chemistry - Complete d-block Question with Solution | TestHub

The$d$-block elements form coloured compounds. These compounds have ions with unpaired electron in$d$-subshell.

i) Na and Mg belong to$s$-block , so NaCl and${\mathrm{M}\mathrm{g}\mathrm{C}\mathrm{l}}_2$are colourless compounds.

ii)${\mathrm{C}\mathrm{u}\mathrm{F}}_2$

Oxidation state of Cu in${\mathrm{C}\mathrm{u}\mathrm{F}}_2$is +2

${\mathrm{C}\mathrm{u}}^{2+}$=$1s^2,2s^2,2p^6,3s^2,3p^6,4s^0,3d^9$

$\therefore {\mathrm{C}\mathrm{u}\mathrm{F}}_2$in which Cu has one unpaired electron is coloured.

iii )$\mathrm{C}\mathrm{u}\mathrm{I}$

Oxidation state of Cu in$\mathrm{C}\mathrm{u}\mathrm{I}$=+1

${\mathrm{C}\mathrm{u}}^{+}$=$1s^2,2s^2,2p^6,3s^2,3p^6,4s^0,3d^{10}$

It has no unpaired electron. So,$\mathrm{C}\mathrm{u}\mathrm{I}$is colourless.

$\therefore$Only${\mathrm{C}\mathrm{u}\mathrm{F}}_2$is coloured among given choices.