Question

Elements while forming compounds become stable by
A.increasing the energy content
B.Decreasing energy content
C.Mutual repulsion
D.Becoming inert

Answer 1

when it comes to molecules, "stable" roughly translates to "lower in energy"

Answer 2

How is it lower in energy ?

Answer 3

Are you aware of the fact that when an electron is more bound to the nucleus, it has more negative potential energy, and thus less total energy?
\[V=-kQq/r ^{2}\]
When an electron is bound more strongly, r decreases and hence the absolute value of V increases.
In a molecule, bonding electrons are attracted by all the nuclei of the participating atoms. Q increases and r decreases. So, the absolute value of V increases largely. But since it is negative, the net energy is lowered.
Got it?