Question: In 1997 we celebrated the centenary of JJ Thomson’s discovery of the electron. Thomson pictured the atom as being like a currant bun, with electron ‘currants’ embedded in a positively charged ‘bun’. Give a short account of three ways in which our model of matter on a subatomic scale has changed since Thomson’s discovery. For each, state clearly how the model changed, and write a few sentences outlining one piece of evidence that played a part in bringing about the change. My response: I've outline the point, but cannot expand on it, can I have help on the detail: Nuclear atom - Alpha scattering: large angles. Incompatible with bun model. Protons and neutrons in nucleus - Chadwick’s experiment: neutral particle of same mass as H. Quarks (existence of) - Deep inelastic scattering: structure within proton. Momentum of electromagnetic radiation - de Broglie theoretical prediction. Antimatter Anderson’s observation of e - like particle with positive charge. Neutrinos - “Missing” energy in beta decay.