The purple colour of the permanganate ion ${{\text{(MnO}}_{\text{4}}}^{\text{-}}\text{)}$ arises due to the _____.

 

Lanthanoids are ______.

The atomic number of cerium $\left(\mathrm{Ce}\right)$ is $58$. The correct electronic configuration of the ${\text{Ce}}^{\text{3+}}$ ion is _____.

Which is NOT the correct statement about the chemistry of $3\mathrm{d}$ and $4\mathrm{f}$ series elements?