4.4.2.1 Radioactive Decay and Nuclear Radiation

Question 1

Radioactive decay:

Answer 1

• some atomic nuclei are unstable
• the nucleus gives out radiation as it changes to become more stable
• this is a random process called nuclear decay

Question 2

Activity:

Answer 2

• the rate at which a source of unstable nuclei decays
• measured in becquerel (Bq)

Question 3

Count-rate:

Answer 3

the number of decays recorded each second by a detector (e.g. Geiger-Muller tube)

Question 4

Alpha particle:

Answer 4

consists of 2 neutrons and 2 protons - same as a helium nucleus

Question 5

Ionising and penetrating power of alpha particles:

Answer 5

• highly ionising
• weakly penetrating (approx. 5cm of air)

Question 6

Beta particle:

Answer 6

• high speed electron ejected from the unstable nucleus
• a neutron /decays turns into a proton and electron
• electron is ejected and proton stays in nucleus

Question 7

Ionising and penetrating power of beta particles:

Answer 7

• medium ionising
• medium penetration (approx. 50cm of air, sheet of paper)

Question 8

Gamma ray:

Answer 8

• electromagnetic radiation from the nucleus (release of energy)
• particles in nucleus just rearrange

Question 9

Ionising and penetrating power of gamma ray:

Answer 9

• low ionising
• highly penetrating (very far in air, few cm of lead)

Question 10

Neutron:

Answer 10

neutron leaves nucleus (unstable nucleus)

Question 11

What is meant by the random nature of radioactive decay?

Answer 11

can’t predict when particular nucleus will decay next