5 Radioactivity (5.23 - 5.25)

Question 1

radioactive decay

Answer 1

change in an unstable nucleus that can result in the emission of a-particles or b-particles and/or gamma-radiation
- changes are random and spontaneous

Question 2

what happens to the nucleus during a-decay or d-decay

Answer 2

the nucleus changes to a different element

Question 3

why may isotopes of an element be radioactive

Answer 3

excess of neutrons in the nuclues and/or the nucleus being too heavy

Question 4

half life

Answer 4

time taken for half the nuclei of that isotope in any sample to decay

Question 5

effect of a-decay, b-decay and y-emissions on the nucleus

Answer 5

increase of stability and reduction in the number of excess neutrons
(for b-emission, neutron –> proton + electron)

Question 6

alpha decay equation

Answer 6

A,Z:X –> A-4, Z-4: Y + 4, 2: a
right nucleus should have 4 less than the OG nucleon number and 2 less of the OG atomic nuber

Question 7

Beta decay equation

Answer 7

neutron changes into a proton and an electron
- mass number stays the same
- atomic mass increases by one
A, Z:X –> A, Z+1:Y + 0,-1:b

Question 8

gamma decay equation

Answer 8

A, Z:X –> A, Z:X + 0,0:y

Question 9

Smoke detectors how

Answer 9

1. isotope of americium which emits alpha particles is used in smoke alarms
2. alpha radiation ionises the air and allows a small current to flow between two electrodes
3. alpha is weakly penetrating so smoke stops it, the current drops and the alarm goes off

(isotope should be an alpha emitter with a long half-life, doesn’t need frequent change)

Question 10

sterilising medical instruments

Answer 10

gamma radiaiton used to sterilise medical equipment, as it is:
- most penetrating, enough to irradiate all sides of the instrumets (without removing the packaging)

Question 11

sterilising food

Answer 11

Food can be irradiated with gamma radiation in order to kill any microbes that are present on it.
- makes it last longer and reduces risk of food borne infections

Question 12

measuring and controlling thickness of materials

Answer 12

radiation used for tracing thickness
- BETA PARTICLES

1. as materials moves above a beta source, the particles that are able to penetrate it can be monitored using a detector
2. if the material gets thicker, more particles will be absorbed, meaning that less will get through
3. allows machine to make adjustments to keep the thickness of the material constant

Question 13

treatment of cancer

Answer 13

radiotherapy: treatment of cancer using radiation
1. beams of gamma rays are directed at the cancerous tumour
- gamma because can penetrate the body (the beams are moved around to minimise harm to healthy tissue whilst being aimed at tumour)

Question 14

Diagnosis of cancer

Answer 14

A tracer - radioactive isotope - used to track movement of substances, like blood around the body
- PET scan can detect the emissions from a tracer to diagnose cancer and determine the location of a tumour

Question 15

Effects of ionising nuclear radiation on living things

Answer 15

• Cell death
• Tissue damage
• Mutations
• Cancer

Question 16

How are radioactive materials moved, used and stored in a safe way?

Answer 16

In lead lined boxes/containers

Question 17

Safety precautions for all ionising radiation

Answer 17

• reducing exposure time
• increasing distance between source and living tissue
• using shielding to absorb radiation (like lead)