Atom

All substances are made of atoms. An atom is the smallest part of an element that can exist. An element is a substance containing only one type of atom: a sample of sodium contains sodium atoms, while a sample of oxygen contains oxygen atoms.

Atoms are the building blocks of matter. An atom has a tiny central nucleus, containing protons and neutrons, surrounded by negatively charged electrons. In the GCSE model, these electrons orbit the nucleus at different set distances.