The force between two atoms is the result of repulsion, nucleus-nucleus , and nucleus-electron . At the point of , the forces balance the forces. The most stable arrangement of atoms exists at the point of , when the atoms bond covalently and a forms.

Explanation:

The same charges repel each other while opposite charges attract each other. During electron-electron interaction repulsion take palace because the electron has negative charges. Nucleus has positive charges so the interaction between two nucleus results in the form of repulsion. When interaction takes place between nucleus and electron then attraction takes place between nucleus and electrons due to opposite charges.

          The formation of a bond that takes place due to the sharing of the electrons is known as a covalent bond and thus the covalent molecule is formed.

c, liquids evaporate, creating a gas