Why does He atom have a smaller radius than the Ne atom?

Answer 1

The size of an atom is not easily measured, or even described, because it does not have an exterior skin that we can measure. Atomic size is therefore generally measured by the distance between the centers of two adjacent atoms.

Because hydrogen exists naturally as a covalent pair bond (H2), the centers of the hydrogen are closer together than helium atoms, which occur freely - helium atoms do not bond to each other.

Answer 2

Hydrogen has one proton, helium has two. Hydrogen has one electron, helium has two, but IN THE SAME ENERGY LEVEL (their average distance from the nucleus is the same). Since the helium nucleus has increased positive charge, the helium electrons are drawn in toward the nucleus (due to electrostatic attraction) than the single electron of hydrogen is to its nucleus. (This is a side effect of imperfect electron shielding).

Answer 3

The He atom only has the 1S shell, while Ne has filled the 1S, 2S, and 2P shells - consequently the electron cloud extends further out from the nucleus of the Neon atom than the electon cloud of the Helium atom.

Answer 4

The atomic radius is determined by the balance between the attraction of the nucleus and the repulsion between electrons. In the case of helium (He), there are fewer electron shells than in neon (Ne), resulting in a smaller atomic radius for helium. Additionally, helium has a higher effective nuclear charge, which pulls the electrons closer to the nucleus compared to neon.

Answer 5

because of higher nuclear charge (greater number of protons) of helium than hydrogen