Question

Which of the following is expected to form colourless complex?

• A. ${Ni}^{2+}$
• B. ${Cu}^{+}$
• C. ${Ti}^{3+}$
• D. ${Fe}^{3+}$

Answer 1

The correct option is B ${Cu}^{+}$

$C{u}^{+}$ is colourless

D block elements of periodic table are called as Transition elements. Transition elements have partially filled d orbitals. The colour for the elements of D block is due to transition of electrons which is called as d -Transition for which presence of partially filled d electrons is must.

copper Cu , has 29 electrons.

so electronic configuration will be $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}3d^{10}$

but in case of $C{u}^{+}$ ion, 28 electrons so:

electronic configuration will be $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}$

$C{u}^{+}$ ion will loose its $4s^1$ electron, and as it has filled $3d^{10}$ orbital,therefore no transition and hence $C{u}^{+}$ ion will not have any colour.