Import Question JSON

$\text{Paramagnetic behaviour} \propto \text{Number of unpaired electrons.}$ $\text{1. The d-block element exhibit a large number of oxidation states than the f-block element. It is because they can lose electron from both 'd' as well as 's' orbital.}$ $\text{Thus, 3d elements show more oxidation states than 4f series elements.}$ $\text{2. According to Aufbau principle, electrons first occupy the lowest energy orbital available to them and enter into higher energy orbitals only after the lower energy orbitals are filled.}$ $\text{Therefore, 3d orbital is higher in energy than 4s. And hence electrons fill up in 4s before filling up in 3d.}$ $\text{But, the energy difference between these subshells is not very high.}$ $\text{3. Europium (II) has electronic configuration [Xe]4f}^7\text{5d}^0 \text{while cerium (II) has electronic configuration [Xe]4f}^2\text{5d}^0.}$ $\text{In Eu(II), subshell is half filled and 5d-subshell is empty.}$ $\text{Since half filled and completely filled electronic configuration are more stable, Eu(II) ions is more stable than Ce(II) in which neither 4f subshell nor 5d subshell is half filled or completely filled.}$ $\text{4. The paramagnetic character in 3d series elements first increases from Sc to Mn as the number of unpaired electrons increases and then decreases as the number of unpaired electrons decreases from Fe to Cu.}$ $\text{Hence, option fourth is the correct answer.}$