1. RUTHERFORD’S EXPERIMENT How he found out how atoms were put together

2. In 1911 it was known that things were made from atoms, and that atoms had positive (+) and negative (-) charges.

3. They thought that atoms were solid little balls of positive charge, with even smaller electrons of negative charge stuck in them.

4. This was the “Plum Pudding” model Spread out positive charge Electron (negative charge)

5. In 1911 Rutherford designed an experiment to find out about the structure of an atom. He fired alpha particles at a very thin piece of gold leaf.

6. gold leaf detector alpha particles He expected them all to go straight through…….

7. gold leaf detector alpha particles But some bounced straight back………….

8. gold leaf detector alpha particles And some were deflected………….

9. From this he worked out two things……..

10. 1. Atoms were mostly empty space apart from a solid centre, or nucleus.This is why some particles bounced back.

11. Empty space Solid nucleus

12. 2. The nucleus has a positive charge, which is why the positively charged alpha particles are repelled if they get too close.

13. Empty space Solid nucleus Repelled by positively charged nucleus

14. If the nucleus has all the positive charge, then the negatively charged electrons must be away from the nucleus.

15. This is how we get Rutherford’s model of the atom Electron (negative charge) Positive charge concentrated at the centre