Scientific models of the atom

• Dalton atoms (1804) – spherical atoms that cannot be split up to explain the properties of gases and the formulae of compounds
• Plum pudding model (1897) – it was found that the mass of electrons, which had recently been discovered, was very much less than the mass of atoms so they must be sub-atomic particles
• the nuclear atom (1911) – an experiment which showed that most of the alpha particles directed at thin gold foil passed through but a few bounced back, suggesting the positive charge was concentrated at the centre of each gold atom
• Discovery of neutrons in the nucleus (1932) – explained why the mass of atoms was greater than could be accounted for by the mass of the protons.
• Periodic Table - An arrangement of elements based on their atomic number and electronic structure.