P7.2 The discovery of the nucleus

Question 1

Why was the Rutherford experiment conducted in a vacuum?

Answer 1

To prevent air molecules absorbing the alpha particles

Question 2

What did Rutherford’s experiment show?

Answer 2

Showed that most of the alpha particles passed straight through

1 in 10000 alpha particles were deflected by more than 90 degrees

Question 3

What did he deduce about the centre of the atom?

Answer 3

Much smaller than the atom because most particles pass through the atom without deflection

Most of the mass was located in the centre

Question 4

Why was rutherford nuclear model of the atom quickly accepted?

Answer 4

Agreed exactly with the measurements Geiger and Marsden made in their experiment

Predicted the existence of the neutron

Explained radioactivity in terms of changes that happen to an unstable nucleus when it emits radiation

Question 5

What was the plum pudding model?

Answer 5

Positively charge matter evenly spread about and electrons buried inside

Question 6

What did Niels Bohr find?

Answer 6

He found that the electron orbits the atom at specific distances and specific energy values or levels