Question

The helium atom has $2$ electrons in its valence shell but its valency is not $2$, Explain.

Answer 1

Valency;- Valency is defined as the tendency of an element to accept extra electrons from other atoms or to give its own extra electrons.

Valency is the ability of an atom in an element to attach to a certain number of other atoms.

Valency of Helium$\left(\mathrm{He}\right)$:

1. Helium is a noble gas or inert gas group member.
2. Noble gases are the most stable elements in the aperiodic table due to having the fully filled outermost orbital or complete octet /duplet with Helium.
3. Helium has a highly stable electronic configuration.${\text{He(z = 2) = 1s}}^2$
4. A Helium atom has only one shell (K shell) which can have a maximum of 2 electrons. It can neither lose electrons nor gain electrons.
5. Helium doesn’t lose or gain any electron from its valence shell.

Hence, the valency of helium is zero.