**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.