**HIGHER TIER: Any reference to H₂O, NH₃, CH₄, O₂, N₂ or CO₂ bonding is higher tier.**

A covalent bond is formed when two atoms share electrons to obtain a noble gas configuration. Covalent bonding occurs between non-metal atoms.

Covalent bonds are strong and require substantial amounts of energy to break.

Covalent bond: a shared pair of electrons.

Molecule: two or more atoms covalently bonded together.

Diatomic: two atoms covalently bonded together in a molecule. O₂, N₂ and Cl₂ are examples of diatomic molecules.