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Which types of elements most often form covalent bonds?

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Diagram showing the formation of a polar covalent bond in a water molecule, with two hydrogen atoms bonding to one oxygen atom to form H2O, illustrating shared electrons and chemical reaction. — covalent bond In polar covalent bonds, such as that between hydrogen and oxygen atoms, the electrons are not transferred from one atom to the other as they are in an ionic bond. Instead, some outer electrons merely spend more time in the vicinity of the other atom. The effect of this orbital distortion is to induce regional net charges that hold the atoms together, such as in water molecules.

Covalent bonds are most often formed between nonmetals. These elements are located toward the right side of the periodic table.1

Because nonmetals have relatively high ionization energies, their atoms are reluctant to lose electrons to form ions. When two nonmetals interact, neither atom can easily strip electrons from the other; instead, they share pairs of electrons to achieve a more stable configuration, resulting in a covalent bond.123

In contrast, when a metal is involved in a compound, the low ionization energy of the metal typically leads to the formation of ionic bonds rather than covalent ones.13