(4) Atoms and Nuclear Radiation

Question 1

What is radioactivity?

Answer 1

The property possessed by unstable nuclei, where they spontaneously emit radiation by the decay of the parent nuclei

Question 2

What is ionisation?

Answer 2

The process of knocking off electrons from an atom

Question 3

Describe the three types of radiation:

Answer 3

• Alpha (made up if 2 protons and 2 neutrons-helium nucleus)
• Beta (an electron emitted by a nuclei)
• Gamma (electromagnetic wave -photon)

Question 4

Why do unstable nuclei give out radiation?

Answer 4

To become more stable, releasing radiation increases stability

Question 5

What is the activity if an unstable nucleus?

Answer 5

The rate of decay

Question 6

What is count rate and how can we measure it?

Answer 6

• the number of radioactive decays per second for a radioactive source
• we mesure count rate using the Geiger-muller tube

Question 7

Name the unit of radioactive activity:

Answer 7

Becquerel (Bq)

Question 8

What is the penetration for the three radiations?

Answer 8

• Alpha (can’t get through skin or paper but highly ionising)
• Beta (stopped by aluminium foil or several meters of air and medium ionisation)
• Gamma (stopped by lead or a few meters of concrete but low ionisation)

Question 9

What is the half life for a radioactive isotope?

Answer 9

• The time it takes for half the sample of unstable nuclei to decay

-count rate after n half lives = initial count rate / 2^n

Question 10

Nuclear equation of alpha radiation:

Answer 10

-The mass number decreases by 4
-The atomic number decreases by 2

Question 11

Nuclear equation of beta radiation:

Answer 11

-The atomic number increases by 1