P2 - Atomic Structure

Question 1

What was the old model for an atom?

Answer 1

The plum pudding model.

Question 2

Describe the plum pudding model.

Answer 2

The positive charge is spread out all over the atom and there are negative “bits” stuck in the positive sphere. It said the mass was spread out over the atom

Question 3

How was the plum pudding model disproved?

Answer 3

Rutherford’s Scattering Experiment. He fired alpha particles which had a +2 charge through the atom toward a gold leaf. He expected them to go straight through but he observed some were deflected a lot, some a little and a few even backwards. They were repelled by the nucleus.

Question 4

Why was it rare for an alpha particle to bounce backwards during the Rutherford Scattering Experiment?

Answer 4

The nucleus providing the repulsive force was tiny.

Question 5

Describe our model of the atom today.

Answer 5

The nuclear model says the positive charge is concentrated in the nucleus.
The mass is concentrated in the nucleus.
Electrons carrying a negative charge orbit the nucleus.
The nucleus is very small compared with the rest of the atom.

Question 6

How is an ion formed?

Answer 6

Atoms normally have an equal number of protons and electrons so they are neutral. An ion is formed when an atom loses or takes in electrons so it has a charge. One cause of this is from IONISING RADIATION.

Question 7

What is the danger of ionising radiation?

Answer 7

It can mutate your cells; giving them extra or taking away electrons. This can cause cancer.

Question 8

Define mass number.

Answer 8

The number of protons and neutrons in an atom.

Question 9

Define atomic number.

Answer 9

The number of protons in an atom.

Question 10

Define an isotope.

Answer 10

They have the same number of protons but a different number of neutrons.