Topic 3 - Radioactivity and Astronomy Flashcards Preview

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discuss J.J Thompsons theory of the atom

1897 Thompson discovered that electrons could be removed from atoms and therefore atoms must be made up of smaller bits.
He suggested the plum pudding model - that atoms where spheres of positive charge with negative electrons stuck in them like fruit in a plum


who disproved the plum pudding theory

In 1909 Rutherford and Marsden tried firing beams of alpha particles at thin gold foil. From the plum pudding model they expected them to pass straight through the sheet or only be slightly deflected.
Most particles went straight through the sheet but some were deflected more than expected and some came straight back the same way.

Rutherford realised this meant most of the mass of the atom was concentrated at the centre in a tiny nucleus and most of an atom is empty space