Past Exam Questions

Question 1

Define radioactivity.

Answer 1

The spontaneous breaking up of unstable nuclei with the emission of one or more types of radiation

Question 2

What change takes place in the structure of the nucleus of an atom when beta decay occurs?
3 points

Answer 2

A neutron in an unstable nucleus is converted into a proton and an electron
Atomic number increases by one
Mass number remains the same

Question 3

Write a balanced equation for the beta decay of a carbon-14 nucleus

Answer 3

14C -> 14N + e-

carbon-14 -> nitrogen-14 + e-

Question 4

What are isotopes?

Answer 4

Atoms of the same element i.e. have the same atomic number which have different mass numbers due to the different number of neutrons in the nucleus

Question 5

What is a radioisotope?

Answer 5

A radioactive isotope

Question 6

Define the half-life of a radioisotope.

Answer 6

The time taken for half of the nuclei in any given sample to decay

Question 7

Give two differences between chemical reactions and nuclear reactions.

Answer 7

No new element is formed in a chemical reaction but a new element is formed in a nuclear reaction
There is no release of nuclear radiation in a chemical reaction but there is nuclear radiation released in a nuclear reaction

Question 8

Give two properties of beta-particles

5 possible points

Answer 8

They are fast moving electrons
They are formed when a neutron in an unstable nucleus changes into a proton and an electron, this electron is then ejected from the nucleus as a beta-particle
They are lighter than alpha particles
They have a higher penetrating power than alpha particles
Can penetrate up to 5 mm of aluminium

Question 9

State one risk associated with exposure to alpha radiation.

Answer 9

Ingestion or inhalation of alpha particles can damage the lungs, liver and kidneys and cause cancer

Question 10

Explain why the occupants of a house fitted with smoke detectors containing americum-241 are not at risk from alpha radiation emitted by these devices.

Answer 10

Alpha particles cannot penetrate the skin and is stopped by a few centimetres of air

Question 11

Explain whether or not the americum-241 in smoke alarms needs to be replaced regularly.

Answer 11

The half-life of americum-241 is 432 years and therefore it does not to be replaced regularly

Question 12

Give two properties of alpha particles

6 possible points

Answer 12

They are groups of two protons and two neutrons stuck together
They carry a double positive charge
They are emitted from the unstable nucleus of a radioactive element
They have a relatively large mass
They travel relatively slow
They have a low penetrating power and are stopped by a sheet of paper or a few centimetres of air

Question 13

Write an equation for the nuclear reaction involved in the beta decay of carbon-14

Answer 13

14C -> 14N + e-

carbon-14 -> nitrogen-14 + e-

Question 14

Explain how the carbon-14 isotope allows certain archaeological discoveries to be dated
3 points

Answer 14

Carbon-14 decays by beta radiation but is continuously replaced when an organism is alive
When an organism dies the amount of carbon-14 present decreases but the amount of carbon-12 remains the same
Therefore, by measuring the ratio of carbon-14 to carbon-12 in the remains of a material scientists can date an object.

Question 15

List the three types of radiation in order of increasing penetrating power

Answer 15

Alpha particles, beta particles, gamma radiation