Radioactivity

Question 1

Define ‘radiation’

Answer 1

Transmission of radiant energy

Question 2

Define ‘radioactivity’

Answer 2

Spontaneous emission of radiation from an atom, in order to form a more stable configuration

Question 3

Define ‘isotope’ (of an element)

Answer 3

An atom with the same atomic number (Z) of the given element, but different mass number (A)/number of neutrons

Question 4

Define ‘half-life’

Answer 4

The time taken for the activity of a radioactive substance to fall by half

Question 5

Describe alpha decay and its effects on an atom

Answer 5

Alpha decay is the emission of a helium nucleus (2 protons and 4 neutrons) by a radioactive atom

It decreases the atomic number (Z) by 2 and mass number (A) by 4

Question 6

Describe positron emission and its effects on an atom

Answer 6

Positron emission is the emission of the positively charged component of a proton (positron) to form a neutron

This decreases atomic number (Z) by 1, but mass number (A) remains unchanged

Question 7

Describe beta decay and its effect on an atom

Answer 7

Beta decay is the emission of a negatively charged electron from a neutron to form a proton

This increases the atomic number (Z) by 1, whilst the mass number (A) is unaffected.

Question 8

What conditions cause positron emission?

Answer 8

A neutron deficit, to create more neutrons to compensate

Question 9

What conditions causes beta decay?

Answer 9

A neutron abundance, to decrease the number of neutrons in the nucleus

Question 10

When does gamma decay occur?

Answer 10

Gamma rays are released due to a nucleus being in a metastable state and are emitted stablise it.

They’re usually released as a result of other radioactive decay too.

Question 11

Describe gamma decay and its effect on an atom

Answer 11

A gamma ray photon is emitted to release energy from an excited nucleus (metastable). No particles are emitted so the atomic make-up is unaffected.

Question 12

A carbon (Z=6, A=12) atom undergoes alpha decay - what is the result?

Answer 12

A new atom with Z=4 and A=8 is created (Berylium)

Question 13

An oxygen atom (Z=8, A=16) undergoes alpha decay - what is the result?

Answer 13

A new atom with Z=6 and A=12) is created (Carbon)

Question 14

What constitutes ‘ionising’ radiation?

Answer 14

Ionising radiation has enough energy to eject an electron from a target, resulting in ion formation

Question 15

Name 3 natural sources of radiation, with examples

Answer 15

Cosmic Radiation - solar flares from the sun
Terrastial radiation - radiation from radon, granite and uranium
Internal - ingested radiation from bananas, brazil nuts and carbon-14

Question 16

Name a source of man-made ionising radiation

Answer 16

X-rays produced from an x-ray tube

Question 17

Which 2 groups are likely to be exposed to man-made radiation?

Answer 17

• Occupationally exposed (radiographers)

- Patients of radiology