Radioactivity

Question 1

What is an isotope?

Answer 1

Atoms of a particular element with the same number of protons but different numbers of neutrons

Question 2

What happens when an electron absorbs EM radiation?

Answer 2

It moves from a lower to higher orbit

Question 3

What happens when an electron emits EM radiation?

Answer 3

It moves from a higher to lower orbit

Question 4

How can electrons leave an atom?

Answer 4

• Absorbing enough EM radiation so they can escape the pull of the atom
• Being hit by a particle such as an alpha or beta particle

Question 5

When will unstable nuclei decay?

Answer 5

When alpha, beta, gamma or neutron radiation is emitted

Question 6

How does an nucleus change when it undergoes alpha decay?

Answer 6

The mass number decreases by 4 and the proton number decreases by 2

Question 7

How does an nucleus change when it undergoes beta+ decay?

Answer 7

The mass number stays the same but the proton number decreases by 1

Question 8

How does an nucleus change when it undergoes beta- decay?

Answer 8

The mass number stays the same and the proton number increases by 1

Question 9

In beta- decay, what decays?

Answer 9

A neutron into a proton and an electron

Question 10

In beta+ decay, what decays?

Answer 10

A proton into a neutron and a positron

Question 11

What are the properties of alpha radiation?

Answer 11

• Very ionising
• Stopped by a sheet of paper
• Travels around 5cm in air

Question 12

What are the properties of beta radiation?

Answer 12

• Mildly ionising
• Stopped by aluminium that is 3mm thick
• Travels a few metres in air

Question 13

What are the properties of gamma radiation?

Answer 13

• Weakly ionising
• Stopped by thick lead
• Travels a few kilometres in air

Question 14

What are the sources of background radiation?

Answer 14

• Radon gas 50%
• Ground and buildings 14%
• Medical 14%
• Nuclear power 0.3%
• Cosmic rays 10%
• Food and drink 11.5%
• Other 0.2%

Question 15

How can radiation be measured?

Answer 15

Using a Geiger-Müller tube

Question 16

How can radiation be detected?

Answer 16

Using photographic film, if radiation is present the photographic film will darken

Question 17

What is the ‘plum pudding model’?

Answer 17

A model of the atom where there are negatively charged ‘electron plumbs’ embedded in a positively charged ‘dough’

Question 18

What was Rutherford’s model?

Answer 18

Rutherford’s model had a positively charged nucleus which the electrons orbited

Question 19

What is the Bohr model?

Answer 19

Electrons orbit a positively charged nucleus, in well defined energy levels, he stated that they could move between energy levels if they gained or lost energy

Question 20

What does the activity of a radioactive source measure?

Answer 20

The amount of atoms that decay every second

Question 21

What does the activity of a source depend on?

Answer 21

The amount of unstable atoms there are

Question 22

What is half-life?

Answer 22

Time it takes for half of the unstable atoms to decay

Question 23

What is activity measured in?

Answer 23

Becquerel (Bq)

Question 24

If a source has an activity of 240Bq what will it’s activity be after 2 half-lives?

Answer 24

240/2 = 120 120/2 = 60Bq

Question 25

What are the uses of gamma rays?

Answer 25

- Kill cancer cells - Diagnose cancer - Preserve food

Question 26

What is the main use of alpha particles?

Answer 26

In smoke alarms

Question 27

What is the main use of beta particles?

Answer 27

To control the thickness of paper

Question 28

What is the danger of ionising radiation?

Answer 28

Ionising radiation causes atoms to turn into ions, these are very harmful to humans and can cause mutations which can lead to cancer

Question 29

What precautions can be taken when coming into contact with ionising radiation?

Answer 29

- Limiting time of exposure - Wearing protective clothing - Increasing the distance between the person and the radioactive source

Question 30

What is irradiation?

Answer 30

Ionising radiation from an external radioactive source travelling to the body

Question 31

What is external contamination?

Answer 31

When radioactive materials come into contact with a person's hair, skin, or clothing

Question 32

What is internal contamination?

Answer 32

When a radioactive source is eaten or drunk

Question 33

How do PET scanners work?

Answer 33

- Patient given a radioactive tracer that decays quickly by emitting positrons - The positrons come into contact with electrons in the body, the two particles annihilate each other forming gamma rays - These gamma rays are detected by a PET scanner and processed by a computer to produce an image on a screen - The tracers need to be put into the body close to where they're used as they decay quickly

Question 34

How are tumors treated using gamma rays?

Answer 34

- Several beams of gamma rays are fired from different positions towards the cancer - Each beam damages the tumor but doesn't kill it - Moving the beam ensures not too much ionising radiation comes into contact with the surrounding tissue

Question 35

How are tumors treated internally?

Answer 35

- By injecting the radioisotope into the patient | - The patient eating or drinking something containing the radioisotope

Question 36

What are the different types of nuclear reactions that can be a source of energy?

Answer 36

- Radioactive decay - Nuclear fission - Nuclear fusion

Question 37

What nuclear fusion?

Answer 37

The fusing of two smaller nuclei to form a larger nuclei, this is what happens in the sun

Question 38

What is nuclear fission?

Answer 38

When an unstable nuclei splits into two smaller ones resulting in huge amounts of energy being released

Question 39

Is nuclear power efficient?

Answer 39

Yes, but nuclear power stations produce radioactive nuclear waste which can stay radioactive for thousands of years

Question 40

What are the advantages of nuclear power?

Answer 40

- Carbon dioxide isn't produced so it doesn't contribute to climate change - Supplies of nuclear fuels

Question 41

What are the disadvantages of nuclear power?

Answer 41

- It's expensive to store nuclear waste safely - If an accident in a nuclear power station happens it can spread radioactive material over a large area - Many people don't want nuclear power stations to be built as they think that nuclear power is dangerous

Question 42

When does a uranium-235 nucleus split?

Answer 42

When it absorbs a neutron

Question 43

What does the fission of uranium-235 produce?

Answer 43

Two daughter nuclei and two or more neutrons

Question 44

When neutrons are released following nuclear fission, other nuclei may absorb them and undergo fission, what is this called?

Answer 44

A chain reaction

Question 45

How is electrical energy generated from power stations?

Answer 45

- Fuel rods containing uranium undergo nuclear fission and thermal energy is released - Thermal energy is used to heat water and produce steam - The steam causes turbines to rotate which turn the generator so it generates electricity - The steam is cooled back into water in a cooler so it can be used again - Extra thermal energy is released by cooling towers or into the sea

Question 46

How are chain reactions controlled?

Answer 46

Using control rods that absorb neutrons

Question 47

Why is nuclear fusion not a suitable source of energy?

Answer 47

It can only occur at very high temperatures and pressures because of electrostatic repulsion happens normally

Question 48

Does nuclear fusion or fission happen in the sun?

Answer 48

Fusion, hydrogen nuclei are converted to helium nuclei