Question

which of the following elements has the smallest atomic radius? argon (ar) neon (ne) helium (he) krypton (kr)

Explanation:

Atomic radius generally decreases across a period and increases down a group in the periodic table. Helium is in the first - period, neon in the second, argon in the third, and krypton in the fourth. As we move down the noble - gas group, the number of electron shells increases, leading to a larger atomic radius.

Answer:

Helium (He)