Question

Select incorrect statement.

• A. Ionisation energies of 5d-elements are greater than those of 3d and 4d elements.
• B. Cu(I) is diamagnetic while Cu(II) is paramagnetic.
• C. $\left[Ti\right(H_{2}O{)}_6{]}^{3+}$ is coloured while $\left[Sc\right(H_{2}O{)}_6{]}^{3+}$ colourless.
• D. Transition elements cannot form complexes.

Answer 1

The correct option is D Transition elements cannot form complexes.

d-block elements have high tendency to form complexes because of their small size, high effective nuclear charge and availability of vacant d-orbital. Therefore they accept lone pair of electrons of ligands in their vacant dorbitals and forms complexes.

As we know, magnetic moment $=\sqrt{n(n+2)}$, where n is no. of unpaired electron.
So Cu (II) is paramagnetic as it has one unpaired electron.

Ionisation energies of 5d-elements are greater than those of 3d and 4d elements because of high nuclear charge as they have almost same radius due to lanthanide contration.

$\left[Ti\right(H_{2}O{)}_6{]}^{3+}$ is coloured because here $T{i}^{3+}$ ion has unpaired electrons while in other complex the central metal ion is $S{c}^{3+}$ does not contain unpaired electrons hence it is colourless.