Question

Which of the following is colored compound?

• A. $Cu{F}_2$
• B. $CuI$
• C. $NaCI$
• D. $MgC{l}_2$

Answer 1

Answer: (A)

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 $MgC{l}_2$ are colourless compounds.
(ii) $Cu{F}_2$ oxidation state of $Cu$ in $Cu{F}_2$ is $+2$
$C{u}^{2+},=1s^2,2s^2,2p^6,3s^2,3p^6,4s^0,3d^9$

$\therefore$ CuF ${}_2$ in which Cu has one unpaired electron is coloured.
(iii) CuI Oxidation state of $Cu$ in CuI $=+1$
$C{u}^{+}-1s^2,2s^2,2p^6,3s^2,3p^6,4s^0,3d^{10}$
It has no unpaired electron. So CuI is colourless.
$\therefore$ Only $Cu{F}_2$ is coloured among given choices.