Chemistry - f-block Question with Solution | TestHub

Lanthanoids are the $\mathrm{f}-$block elements and $4\mathrm{f}$ series element. The orbital size of the $4\mathrm{f}$ is much bigger due to which electrons are spread in the large area, these electrons not able to shield charge from the nucleus. As a result, the poor screening effect or poor shielding effect of the $4\mathrm{f}$ sub-shell. There is regular decrement of the atomic radius on increasing the atomic number.