Molecule

Small molecular substances contain separate molecules with fixed numbers of atoms. The formula H₂O identifies two hydrogen atoms and one oxygen atom in each water molecule; other common examples include H₂, Cl₂, O₂, N₂, HCl, NH₃, CH₄ and CO₂. To deduce a molecular formula from a model, identify one complete molecule, count the atoms of each element and write those actual counts as subscripts.

In a simple molecular substance, covalent bonding produces molecules: separate particles, each containing a fixed number of covalently bonded atoms.

A simple molecular substance consists of separate molecules. Each molecule contains a fixed, relatively small number of atoms joined by covalent bonds.

A chemical formula uses these symbols to describe a substance. It tells you which elements are present and how many atoms of each element occur in a molecule. A formula is not an abbreviation that can be written in several different ways: changing a symbol, its capitalisation or a subscript can change the substance represented.