Nuclear chemistry

Question 1

Describe radioactive decay

Answer 1

Radioactive decay is the process by which unstable atomic nuclei become stable by emitting radiation in the form of alpha, beta, or gamma radiation. This process helps the nucleus lose energy and reach a more stable state.

Question 2

Describe the properties of alpha particles

Answer 2

Alpha Particles
Charge: Positively charged; attracted to a negative plate.
Penetration: Low penetration power; can only travel a few centimeters and are easily stopped by paper.

Question 3

State the definition of a half-life

Answer 3

Half-life is the time required for half of the radioactive nuclei in a sample of a particular isotope to decay.

It is constant and remains unaffected by chemical or physical conditions.

Question 4

Describe the properties of beta particles

Answer 4

Beta Particles
Nature: Electrons emitted from the nucleus.
Charge: Negatively charged; attracted to a positive plate.
Penetration: Moderate penetration power; can travel about 1 meter but are stopped by a thin sheet of aluminium.

Question 5

Describe the properties of Gamma rays

Answer 5

Gamma Rays
Nature: Electromagnetic waves with no mass or charge.
Charge: Not affected by charged plates due to having no charge.
Penetration: High penetration power; can travel long distances and are stopped only by thick barriers of lead or concrete.

Question 6

State some uses of radioactive isotopes

Answer 6

Exam Tip
You do not need to know specific examples but should be able to explain why a particular radioisotope is suitable for a given application.

For example, in smoke detectors, a long half-life is preferred so it doesn’t need frequent replacement, and alpha radiation is chosen because it does not travel far.
In medical tracers, the half-life should not be too short (to ensure detection is possible) but also not too long (to avoid prolonged radiation exposure in the body).