C3.2.2 - Looking into Atoms

Question 1

How did John Dalton imagine atoms?

Answer 1

They looked like small snooker balls.

Question 2

What did J. J. Thomsons cathode ray tube experiment show?

Answer 2

That atoms were not made from a single particles. They contained negatively charged electrons in a positivly charged sphere (like a plum pudding)

Question 3

What was J. J. Thomsons atomic model called?

Answer 3

The plum pudding model

Question 4

What does the diagram show?

Answer 4

J. J. Thomson’s Plum Pudding Model of a single atom

Question 5

Who disproved J. J. Thomson’s plum pudding model of the atom?

Answer 5

Ernest Rutherford

Question 6

Describe Ernest Rutherford’s gold foil experiment that disproved the ‘plum pudding model’

Answer 6

1. Positive alpha particles were fired at gold foil.
2. A fluorescent screen identified electrons that had passed through the foil.
3. Rutherford expected some to pass straight through and some to be deflected slightly by the negative electrons in the atom.
4. Some bounced back off the foil.
5. This showed a positive centre must be causing the electrons to be repelled.
6. There must be space in the atom as some electrons passed through and were not deflected at all.

Question 7

Which atomic model does the diagram show?

Answer 7

Rutherford’s atomic model

Question 8

Describe Rutherfod’s atomic model

Answer 8

• Atoms have a central nucleus with a positive charge.
• There is a big empty space around the nucleus.
• Electrons move around the big empty space.