Why is the helium atom chemically inert?

Answer 1

"Chemically unstable" is ... kind of an odd phrase. Nearly all atoms are "chemically unstable" in the sense that they will react with other atoms (the exception is the noble gases, which react, if at all, only under extreme conditions).

Basically, whether an atom will react or not depends on its outer (valence) electrons. A full set of valence electrons (2 for the first shell, 8 for every shell after that) is particularly stable, so atoms will tend to react in such a way as to form them. Alkali metals will try to lose one electron, halogens will try to gain one electron, and so on. The noble gases already HAVE a full valence shell, so they're quite unreactive.

Answer 2

Helium has completely filled valence electrons (stable electronic configuration) and hence is chemically inert.

Answer 3

It is very inert because the attractive forces in the atom are very strong.

Answer 4

An Atoms "aim" is to get to 8 electrons in its outer shell. It has reached a stable state, once this is achieved. All inert gasses are stable atoms with 8 electrons in their outer shells.