Molecule Facts

  • A molecule is two or more atoms bonded together. It is normally the smallest bit of a substance that exists independently.
  • Hydrogen atoms exist only in pairs, or joined with atoms of other elements. A linked pair of hydrogen atoms is a hydrogen molecule.
  • The atoms in a molecule are held together by chemical bonds (see chemical bonds).
  • The shape of a molecule depends on the arrangement of bonds that hold its atoms together.
  • A carbon dioxide molecule consists of one carbon atom and two oxygen atoms, and has the chemical formula CO2.
  • Ammonia molecules are pyramid shaped; some protein molecules are long spirals.
  • Compounds only exist as molecules. If the atoms in the molecule of a compound were separated, the compound would cease to exist.
  • Chemical formulas show the atoms in a molecule.
  • The formula for ammonia, a kind of gas, is NH 3 — one nitrogen atom and three hydrogen.
  • The mass of a molecule is called the molecular mass. It is worked out by adding the mass of all the atoms in it.