Question

Why do noble gases almost never form chemical bonds?

Answer 1

They already have full valence shells.

Explanation:

Chemical bonds, whether they're ionic or covalent, involve the sharing of electrons so that atoms can have a full "valence shell", which is its outermost layer of electrons. Each new shell is represented by a row on the periodic table.

Noble gases, on the far right, already have full electron shells. Thus, they achieve a low energy level and are content without having to bond.

In contrast, halogens, the second furthest group on the right, want to gain one electron to attain a full valence shell, so they are very reactive.