Elements and Compounds, Atoms and Molecules

Structure of a water molecule

The world around you is made up of elements and compounds, atoms and molecules. But what are these things?

The model of a lithium atom


  • Atoms are tiny particles which make up elements
  • Atoms are particles which cannot be divided further
  • There are currently 118 different elements
  • Atoms of one element are different to atoms of every other type of element


  • Are made up of two or more atoms chemically bonded (joined) together
  • It is not possible to separate the atoms in a molecule without breaking bonds


  • Elements are made up of just one type of atom
  • For example Oxygen, O2, is a molecule made up of Oxygen atoms only and is therefore an element.
  • The periodic table contains all 118 known elements


  • Compounds are molecules made up of more than one type of atom chemically bonded together.
  • For example Water, H2O, which contains 2 Hydrogen atoms and 1 oxygen atom bonded to each other

Structure of a water molecule, a compound containing 1 Oxygen atom bonded to 2 Hydrogen atoms