When none of the elements in a compound is a metal, no atoms in the compound have an ionization energy low enough for electron loss to be likely. In such a case, covalence prevails. As a general rule, covalent bonds are formed between elements lying toward the right in the periodic table (i.e., the nonmetals). Molecules of identical atoms, such as H2 and buckminsterfullerene (C60), are also held together by covalent bonds. In Lewis terms a covalent bond is a shared electron pair. The bond between a hydrogen atom and a chlorine atom in hydrogen chloride is formulated as follows: ...(100 of 27318 words)