# Question #c0a6f

It occurs because of the tendency of the atom to have its valence shell full ($O c t e t$ $r$$u$$l$$e$)
$8$ electron in their valence shell.
In the above example the $o$$x y$$g$$e n$ atom needs $2$ more electrons So,it shares the $2$ electrons from a $o$$x y$$g$$e n$ molecule to for a covalent bond molecule.