A covalent bond is a type of chemical bond that holds different atoms together by sharing electrons. Depending on how equally the electrons are shared between the atom, these bonds may be either polar (having an unequal distribution of charge) or nonpolar (having an equal distribution of charge) in nature. In their most stable form, the outer electron shells of an atom are evenly filled. If there are too many or too few electrons to evenly fill these shells, the atom will try to combine with other atoms to reach a lower energy state that is more stable. By sharing electrons, atoms can achieve greater stability.

Atoms can have varying degrees of attraction for its outer shell, or valence, electrons. This measure of attraction is called electronegativity. An atom with high electronegativity is strongly attracted to its electrons and will try to combine with another atom...