4- Further Developments

Niels Bohr, 1913. 1) Electrons orbit nucleus at fixed distances/different energy levels from nucleus 2) Chemicals burn with certain-coloured flames ∴ the pattern of energy released by electrons in the chemical reaction, must be the same for every single atom of that element James Chanwick, 1912/1932 1) There was a difference between the atomic no. and atomic mass of an atom 2) ∴ there had to be a neutral particle the same size as the proton to keep the nucleus stable and make up the missing mass, scientist accepted this 20 years later - 1932