Atomic structure

Question 1

when does the energy level of an electron change?`

Answer 1

when the atom emits or absorbs electromagnetic radiation

Question 2

what happens when atoms absorb electromagnetic radiation

Answer 2

electrons to a higher energy level

Question 3

what happens when atoms emit electromagnetic radiation

Answer 3

electrons drop to a lower energy level

Question 4

What is radioactive decay?

Answer 4

when isotopes are unstable and decay into other elements and give out radiation as they try to become more stable

Question 5

what does the type of radiation depend on?

Answer 5

why the nucleus is unstable and is spontaneous

Question 6

what are 4 types of nucleur radiation?

Answer 6

alpa beta gamma neutron

Question 7

What is ionising radiation?

Answer 7

radiation that creates positive ions. *the ionising power of radiation source is how easily it can do this

Question 8

What is activity?

Answer 8

the rate at which a source of unstable nuclei decays.

Question 9

what is activity measured in?

Answer 9

becquerel (Bq)

Question 10

What is the count-rate?

Answer 10

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

Question 11

What do alpha particles consist of?

Answer 11

two neutrons and two protons the same as a helium nucleus

Question 12

What is alpha radiation?

Answer 12

when an alpha particle is emitted from the nucleus

Question 13

What are the features of alpha radiation?

Answer 13

• they don’t penetrate very far into materials and are stopped quickly
• they can only travel a few cms in air and are absorbed by a sheet of paper
• because of their size they are strong ionising

Question 14

What is a beta particle?

Answer 14

a high-speed electron ejected from the nucleus as a neutron turns into a proton

Question 15

What are features of beta radiation?

Answer 15

• they are moderately ionising
• they penetrate moderately far into materials before colliding and have a range in air of a few metres.
• they are absorbed by a sheet of aluminium

Question 16

what is a gamma ray?

Answer 16

electromagnetic radiation from the nucleus

Question 17

What are features of gamma radiation?

Answer 17

• they penetrate far into material without being stopped and will travel a long distance through air
• they are weakly ionising because they pass through rather than collide with atoms

* eventually they hit something and do damage

• they can be absorbed bu thick sheets of lead or metres of concrete

Question 18

What happens during beta decay?

Answer 18

a neutron in the nucleus turns into a proton and releases a fast-moving electron

because the nucleus has lost a neutron and gained a proton the mass doesnt change

Question 19

Gamma rays don’t change the charge or mass of the nucleus.

What do they do instead?

Answer 19

They get rid of excess energy from a nucleus

Question 20

Radioactive decay is spontaneous, however, with a _______________ it is possible to predict how many decay in a certain time period

Answer 20

large enough number of nuclei

Question 21

What is half-life?

Answer 21

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 22

What can the half-life be used for?

Answer 22

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 23

The radioactivity of a source decreases over ______

Answer 23

time

Question 24

What happens each time a radioactive nucleus decays?

Answer 24

the activity as a whole will decrease

Question 25

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

Answer 25

• 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 26

long half-life means:

Answer 26

• 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 27

What is radioactive contamination?

Answer 27

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

Question 28

Why is radioactive contamination harmful?

Answer 28

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

Question 29

What precautions are taken against the hazards of radioactive contamination?

Answer 29

• 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 30

What is irradiation?

Answer 30

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

Question 31

How can you reduce of effects of irradiation?

Answer 31

• 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 32

What are the hazards associated with irradiation?

Answer 32

• 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 33

What are the hazards associated with contamination?

Answer 33

• 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 34

What are the uses of nuclear radiation? (3)

Answer 34

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

Question 35

Why would a gamma source make the best tracer?

Answer 35

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