The Model of the Atom

Question 1

What was the plum pudding model?

Answer 1

Suggested by J.J. Thomson, it was the idea that atoms were spheres of positive charge with tiny negative electrons stuck in them

Question 2

What experiment did Rutherford perform that would debunk the plum pudding model?

Answer 2

Firing positive alpha particles at thin gold foil

Question 3

What did Rutherford originally expect from his experiment?

Answer 3

The particles were expected to pass straight through the gold sheet, or only be slightly deflected

Question 4

What results did Rutherford get from his experiment?

Answer 4

• Most particles went straight through the sheet
• Some were deflected more than expected
• A few were deflected back the way they had come

Question 5

What conclusions did Rutherford make because of his experiment?

Answer 5

• Most of the mass of the atom was concentrated at the centre in a tiny nucleus
• Most of an atom is empty space
• The nucleus must have a positive charge as it repelled the positive alpha particles

Question 6

What was the Bohr model?

Answer 6

• Proposed by Niels Bohr, it was a model where the electrons were in fixed orbits at set distances from the nucleus
• These were called energy levels

Question 7

What are the relative masses and relative charges of a proton, neutron and electron?

Answer 7

Question 8

What is approximately the typical size of an atom?

Answer 8

(1 × 10⁻¹⁰) metres

Question 9

Use the relative charges of the subatomic particles to explain why an atom has no overall charge.

Answer 9

• Protons have a positive charge, +1, and electrons have a negative charge, -1
• Because atoms have an equal number of protons and electrons, the charges cancel out, therefore atoms have no overall charge

Question 10

(Exam-style question)

Answer 10

Question 11

(Exam-style question)

Answer 11