Topic 4c- Radioactivity

Question 1

What happens in alpha radiation?

Answer 1

An alpha particle is emmitted- it has two neutrons and two protons (therefore equivalent to a helium atom)

Question 1

Why does a substance undergo radioactive decay?

Answer 1

To become more stable

Question 2

What does an alpha particle consist of?

Answer 2

2 protons and 2 neutrons, therefore it is equal to a helium atom

Question 3

What are the properties of alpha radiation

Answer 3

• highly ionising
• 2-3cm in air
• stopped by paper

Question 4

What does it mean when radiation is ionising?

Answer 4

The radiation causes other partices to loose electrons (ionise)

Question 5

What is beta decay?

Answer 5

• When a nucleus decays by beta decay, a neutron turns into a proton in the nucleus, releasing a beta-particle (a fast moving electron).
• This therefore increases the charge of the nucleus (and the atomic number of the atom) by 1.

Question 6

What are the properties of beta radiation?

Answer 6

• 2-3m in air
• moderately ionising
• absorbed by 5mm aluminium

Question 7

What are gamma rays?

Answer 7

Very short electromagnetic waves
They have no mass and no charge

Question 8

What are the properties of gamma rays?

Answer 8

• Weakly ionising (they tend to pass through atoms rather than collide with atoms)
• can be absorbed by thick sheets of lead or meters of concrete

Question 9

What can radiation be measured with?

Answer 9

A Geiger-Muller tube and counter (records the count rate)

Question 10

What is half-life?

Answer 10

Half-life is the time taken for the number of nuclei of a radioactive isotope in a sample to halve.

Question 11

What does it mean if a radioactive sample has a short half-life?

Answer 11

• radioactivity falls quickly
• can be initially harmful but become safe more quickly

Question 12

What does it mean if a radioactive sample has a long half-life?

Answer 12

• the sample is releasing smalll amounts of radiation over a long period
• this can be very damaging to the surroundings