Question

Is Helium the smallest element?

Answer 1

1. The chemical symbol of Helium is $\mathrm{He}$.
2. It has an atomic radius of only 31 pm.
3. This is due to the tendencies of the periodic table and the effective nuclear charge, which keeps the valence electrons closer to the nucleus.
4. The atomic radius decreases from left to right in a period and from top to bottom in a group.

Hence, Helium is the smallest element.