Atomic Structure

Question 1

What is activity?

Answer 1

The rate at which an unstable nucleus decays. This is in all directions.

Question 2

What is count rate?

Answer 2

The number of decays per second. This measures activity in one direction.

Question 3

What is used to measure radiation?

Answer 3

A Geiger Muller tube.

Question 4

What is the largest source of background radiation?

Answer 4

Radon gas.

Question 5

What is background radiation?

Answer 5

The radiation that is around us all the time.

Question 6

What are some natural sources of background radiation?

Answer 6

• Radon gas
• Cosmic rays

Question 7

What are some man made sources of background radiation?

Answer 7

Medical.

Question 8

What happens when an atom absorbs EM radiation, and what is this process called?

Answer 8

Excitation
An electron moves further from the nucleus.

Question 9

How is electro-magnetic radiation emitted?

Answer 9

De-excitation
An electron moves closer to the nucleus.

Question 10

What is alpha radiation?

Answer 10

A helium nucleus.
2 neutrons and 2 protons.

Question 11

What is beta radiation?

Answer 11

A high energy electron.

Question 12

What is gamma radiation?

Answer 12

An Em wave.

Question 13

What makes an atom radioactive?

Answer 13

Too many protons or neutrons, which make the nucleus unstable.

Question 14

Where in the atom are all types of radiation emitted from?

Answer 14

The nucleus.

Question 15

What is the charge of alpha radiation?

Answer 15

+2

Question 16

How far can alpha radiation travel in air?

Answer 16

5cm

Question 17

What is alpha radiation absorbed by?

Answer 17

Paper

Question 18

How ionising is alpha radiation?

Answer 18

Strongly ionising.

Question 19

What is beta radiation absorbed by?

Answer 19

Aluminium.

Question 20

How far can beta radiation travel in air?

Answer 20

1m

Question 21

How ionising is beta radiation?

Answer 21

Weakly ionising.

Question 22

What is gamma radiation reduced by?

Answer 22

• cm’s of lead
• m’s of concrete

Question 23

How far can gamma radiation travel in air?

Answer 23

Unlimited range.

Question 24

Why are alpha particles the most ionising?

Answer 24

They are the largest.

Question 25

What is neutron emission?

Answer 25

A free neutron.

Question 26

What causes neutron emission?

Answer 26

Spontaneous or induced nuclear fission.

Question 27

How far can neutron radiation travel in air?

Answer 27

1000's of m's

Question 28

What blocks neutron radiation?

Answer 28

**Hydrogen rich materials** - Water - Concrete

Question 29

How can neutron emission be ionising?

Answer 29

By making other atoms unstable and radioactive.

Question 30

What happens to an atom when it emits an alpha particle?

Answer 30

- Mass number decreases by 4 - Atomic number decreases by 2 - It changes into a new element

Question 31

What happens to an atom when it emits an beta particle?

Answer 31

- Mass number remains the same - Atomic number increases by 1 - It changes into a new element

Question 32

Where does the beta particle come from?

Answer 32

A neutron turns into a proton and an electron, the proton remains in the nucleus and the electron is emited.

Question 33

What is half life?

Answer 33

Time for half the nuclei to decay OR Time for the count rate to half

Question 34

Which isotope is used for carbon dating?

Answer 34

Carbon 14.

Question 35

How does carbon 14 end up in plants and animals?

Answer 35

- It combines with oxygen to form radioactive carbon dioxide - Absorbed by plants for photosynthesis - Plants are then eaten by animals

Question 36

Why does the amount of carbon 14 decreases once an organism has died?

Answer 36

It stops exchanging carbon with its atmosphere, and the carbon 14 starts to decay.

Question 37

What is contamination?

Answer 37

Where radioactive atoms get onto materials where they are not wanted.

Question 38

What is irradiation?

Answer 38

When an object is exposed to nuclear radiation.

Question 39

Which type of radiation is used for irradiating food?

Answer 39

Gamma.

Question 40

What is irradiation used for?

Answer 40

- Making food last longer - Sterilising medical equipment

Question 41

Why is irradiating used for some medical equipment insted of heat sterilisation?

Answer 41

High temperatures could melt/damage some components.

Question 42

What are some uses of radiation, and what type of radiation does each use?

Answer 42

- Smoke detectors (alpha) - Thickness control (beta) - Sterilising (gamma) - Medical tracers (gamma) - Industrial tracers(gamma)

Question 43

What property of gamma radiation makes in appropriate for use in radiotheripy?

Answer 43

It can be focused to a point.

Question 44

Why do people wear protective clothing when handling radioactive material?

Answer 44

It prevents contamination.

Question 45

How is radiation used in medicine?

Answer 45

- Tracers (show flow through an organ) - Gamma camera (gamma injected into the body and detected) - Radiotherapy - Implants (Destroying cancer cells)

Question 46

When is alpha radiation dangerous?

Answer 46

When it is inside the body.

Question 47

How do people who work with radiation reduce the risk?

Answer 47

- Distance from the source - Short time near the radiation - Using shielding

Question 48

What is released when a large nucleus splits in nuclear fission?

Answer 48

- Smaller daughter nuclei - More neutrons - Energy - Gamma rays

Question 49

Why do the masses of the of the products of nuclear fission not add up the the mass of the original nuclei?

Answer 49

Some mass is converted to energy.

Question 50

How does a nuclear power station generate electricity?

Answer 50

Heat from the reactor is used to boil water, this steam then turns a turbine which turns a generator.

Question 51

What do the fuel rods contain?

Answer 51

Enriched uranium

Question 52

What is enriched uranium?

Answer 52

Uranium which contains a higher percentage of uranium-235 that the natural ore.

Question 53

What do the control rods do?

Answer 53

They absorb neutrons, and can be moved in and out to control the speed and temperature of the reaction.

Question 54

What are the control rods made from?

Answer 54

Boron/Cadmium

Question 55

What does the moderator do?

Answer 55

Slows down neutron to allow them to be absorbed by the uranium nuclei.

Question 56

What is the moderator made from?

Answer 56

Graphite or water.

Question 57

What does the coolant do?

Answer 57

Water flows around the reactor and transfers thermal energy way from it. This can also act as the moderator.

Question 58

Why does the fuel need to be extremely hot for nuclear fusion?

Answer 58

It has to be made into plasma.

Question 59

Why does the fuel for nuclear fusion need to be plasma?

Answer 59

So that the particles can collide without rebounding due to electrostatic repulsion.

Question 60

What is a plasma?

Answer 60

A gas where the electrons have been stripped from the nuclei.

Question 61

Does fission or fusion release more energy per kg of fuel?

Answer 61

Fusion.

Question 62

What is the fuel for nuclear fusion?

Answer 62

Isotopes of hydrogen which can be made from water and lithium.

Question 63

Which isotopes of hydrogen are used for nuclear fusion?

Answer 63

Deuterium and tritium

Question 64

What condition is neaded for nuclear fusion other than temperature?

Answer 64

High pressure

Question 65

Where does the energy for nuclear fusion come from?

Answer 65

Mass is converted into energy.