The electronic configuration of gadolinium (atomic number of 64) is:

1. $\left[\mathrm{Xe}\right]4{\mathrm{f}}^{3}5{\mathrm{d}}^{5}6{\mathrm{s}}^2$

2. $\left[\mathrm{Xe}\right]4{\mathrm{f}}^{7}5{\mathrm{d}}^{2}6{\mathrm{s}}^1$

3. $\left[\mathrm{Xe}\right]4{\mathrm{f}}^{7}5{\mathrm{d}}^{1}6{\mathrm{s}}^2$

4. $\left[\mathrm{Xe}\right]4{\mathrm{f}}^{8}5{\mathrm{d}}^{6}6{\mathrm{s}}^2$

The most common oxidation state for lanthanoids and actinoids is:

The different oxidation states exhibited by the lanthanoids are:

Lanthanoid's most common oxidation state is:
1. 2
2. 5 
3. 3 
4. 4

Which one of the following is a diamagnetic ion?

Actinoids show a greater number of oxidation states than lanthanoids because:  

The electronic configuration of the last element of actinoids is :

1. Thorium, Th: $\left[\mathrm{Rn}\right]5{\mathrm{f}}^{14}6{\mathrm{d}}^{1}7{\mathrm{s}}^2$

2. Lawrencium, Lr: $\left[\mathrm{Rn}\right]5{\mathrm{f}}^{14}6{\mathrm{d}}^{1}7{\mathrm{s}}^2$

3. Neptunium, Np: $\left[\mathrm{Rn}\right]5{\mathrm{f}}^{14}6{\mathrm{d}}^{1}7{\mathrm{s}}^2$

4. Protactinium, Pa: $\left[\mathrm{Rn}\right]5{\mathrm{f}}^{14}6{\mathrm{d}}^{1}7{\mathrm{s}}^2$

The incorrect statement among the following is: 

The correct statement regarding inner transition elements is: