A covalent bond is a bond that forms when the two atoms share their electrons pretty equally. This is caused by the difference in electronegativity, or ΔEn. When the ΔEn is low, the bond is more covalent. If the ΔEn is high, the bond is more ionic.
A covalent bond is formed when two atoms share electrons. The electrons may be share unequally (a polar bond) if one atom is more electronegative than the other. In this case, the electronegative atom will have a greater share of the electrons. If the difference in electronegativity of the two atoms is negligible, the electrons are shared equally (a nonpolar bond).
