Question

The noble gas with the smallest atomic radius.

Hint:

Remember the periodic trends: electronegativity increases across a period and decreases down a group. Atomic mass generally increases with atomic number. Atomic radius decreases across a period and increases down a group.

Answer 1

Helium, being the lightest noble gas with only two electrons in a single electron shell, has the smallest atomic radius among all noble gases. Due to its small size and the strong attraction between its nucleus (2 protons) and its 2 electrons, helium’s atomic radius is the smallest in its group, around 31 picometers (pm).