1. + Evidence For The Atomic Structure Noadswood Science, 2012

2. + Evidence For The Atomic Structure To understand the Rutherford scattering experiment Sunday, June 12, 2016

3. + Plum Pudding An early model about the structure of the atom was called the plum pudding model In this model, the atom was imagined to be a sphere of positive charge with negatively charged electrons dotted around inside it like plums in a pudding The positively charged matter in the atom was evenly spread about (pudding) The electrons were buried inside (plums)

4. + Disproved Rutherford, the father of nuclear physics, conducted an experiment which proved the plum pudding idea was incorrect Rutherford, along with Geiger and Marsden proved the plum pudding model incorrect with their scattering experiment

5. + Scattering Experiment A beam of alpha particles was aimed at very thin gold foil and their passage through the foil detected

6. + Scattering Experiment A beam of alpha particles was aimed at very thin gold foil and their passage through the foil detected The alpha particles were expected to pass straight through the foil, but instead some of the alpha particles emerged from the foil at different angles, and some even came straight back The positively charged alpha particles were being repelled and deflected by a tiny concentration of positive charge in the atom As a result of this experiment, the plum pudding model was replaced by the nuclear model of the atom

7. + Scattering Experiment

8. + Most of the alpha particles passed straight through the metal foil The number of alpha particles deflected per minute decreased as the angle of deflection increased About 1 in 10’000 alpha particles were deflected by more than 90 o Rutherford said this was like “firing naval shells at cardboard, and discovering the occasional shell rebounds”

9. + Scattering Experiment From this experiment Rutherford concluded that there is a nucleus at the centre of every atom which: - Is positively charged because it repels alpha particles Is much smaller than the atom as most alpha particles passed through it Is where most of the mass of the atom is located The nucleus diameter was found to be about 100’000 times smaller than the atom

10. + Scattering Experiment Alpha particles Thin gold foil Most particles passed through, but 1/10’000 were deflected by more than 90 0

11. + Atomic Structure Electron – negative; mass of 1/2000 th Proton – positive; mass of 1 Neutron – neutral; mass of 1