Atomic structure

Question 1

What is half-life?

Answer 1

the time it takes for the number of nuclei of the isotope in a sample to halve, or the time it takes for the count rate (or activity) from a sample containing the isotope to fall to half its initial level.

Question 2

What can the half-life be used for?

Answer 2

to make predictions about radioactive sources, even though their decays are random

• can also be used to find the rate at which a source decays (activity)

Question 3

The radioactivity of a source decreases over ______

Answer 3

time

Question 4

What happens each time a radioactive nucleus decays?

Answer 4

the activity as a whole will decrease

Question 5

What does it suggest if an isotope has a short half-life?

Answer 5

• the activity falls quickly
• the nuclei are very unstable
• emit radiation very quickly s exposure can be hazardous
• they quickly became safe
• don’t remain radioactive for long

Question 6

long half-life means:

Answer 6

• the activity falls more slowly
• they are more stable and remain radioactive for a long time
• emit radiation slowly so exposure is less hazardous

Question 7

What is radioactive contamination?

Answer 7

the unwanted presence of materials containing radioactive atoms on other materials.

Question 8

Why is radioactive contamination harmful?

Answer 8

because when the contaminating atoms decay, they release radiation which could cause you harm

Question 9

What precautions are taken against the hazards of radioactive contamination?

Answer 9

• Gloves and tongs should be used when handling sources to avoid particles getting stuck to your skin or under your nails

Protective suits can be worn to stop you breathing in the contamination

Question 10

What is irradiation?

Answer 10

The process of exposing an object to nuclear radiation. The irradiated object does not become radioactive.

Question 11

How can you reduce of effects of irradiation?

Answer 11

• keep radioactive sources in lead-lined boxes,
• standing behind barriers
• being in a different room
• not handling sources with bare arms
• using sources of the lowest activity possible for the shortest amount of time possible

Question 12

What are the hazards associated with irradiation?

Answer 12

• Outside the body, beta and gamma sources are the most dangerous. This is because the beta and gamma can penetrate the body and get to delicate organs
• Alpha is less dangerous because it has the least penetration and therefore can’t penetrate the skin and is easily blocked by a small gap
• Alpha wouldn’t be dangerous unless entered into, but an area with gamma can irradiate people near by

Question 13

What are the hazards associated with contamination?

Answer 13

• Alpha is the most dangerous inside the body because they are the most ionising and they do all their damage in a very localised area
• Beta sources are less damaging inside the body as radiation is absorbed over a wider area and some passes out of the body altogether
• Gamma sources are the least dangerous because they just pass straight out- the lowest ionising power

Question 14

What are the uses of nuclear radiation? (3)

Answer 14

• medical tracers
• looking for damages or blockages in the intestine
• treating tumours

Question 15

Why would a gamma source make the best tracer?

Answer 15

• they can penetrate the body and be detected on the outside
• they are the least ionising