Chemistry - f-block Question with Solution | TestHub

Protactinium $\left(\mathrm{Pa}\right)$ is the element that does not have stable electronic configuration.

Protactinium $\left(\mathrm{Pa}\right)=\left[\mathrm{Rn}\right]5{\mathrm{f}}^{2}6{\mathrm{d}}^{1}7{\mathrm{s}}^2$ (Atomic number $=91$)

Nobelium $\left(\mathrm{No}\right)=\left(\mathrm{Rn}\right)5{\mathrm{f}}^{14}6{\mathrm{d}}^{0}7{\mathrm{s}}^2$ (Atomic number $=102$)

Lawrencium $\left(\mathrm{Lr}\right)=\left[\mathrm{Rn}\right]5{\mathrm{f}}^{14}6{\mathrm{d}}^{1}7{\mathrm{s}}^2$ (Atomic number $=103$)

Americium $\left(\mathrm{Am}\right)=\left[\mathrm{Rn}\right]5{\mathrm{f}}^{7}6{\mathrm{d}}^{0}7{\mathrm{s}}^2$ (Atomic number $=95$)