Atoms And Radioactivity

Front 1

Who came up with the nuclear model of the atom?

Back 1

Scientists Rutherford and Marsden.

Front 2

Describe the nuclear model of the atom.

Back 2

1) The nucleus is tiny, but it makes up most of the mass of the atom. It contains protons and neutrons and the nucleus has an overall neutral charge.

2) The rest of the atom is mostly empty space.
3) Negative electrons orbit around the nucleus.

Front 3

Where do radioactive substances give out radiation from?

Back 3

The nuclei of their atoms.

Front 4

True or false:
The process of nuclear decay is entirely random.

Back 4

True. You can't say when any nuclei will decay and you can't do anything to make it happen.

Front 5

What is radioactive decay NOT affected by?

Back 5

Physical conditions like temperature or by any sort of chemical bonding.

Front 6

Name the three types of radiation that atoms emit.

Back 6

Alpha, beta, gamma

Front 7

List the sources that background radiation comes from.

Back 7

1) Radon gas

2) Food

3) Cosmic rays

4) Medical x-rays

5) Rocks and building materials

6) Nuclear industry

Front 8

What is background radiation?

Back 8

Radiation that is present at all times, all around us - most of this is from natural sources.

Front 9

What is the radiation that comes from space called?

Back 9

Cosmic rays (cosmic radiation)

Front 10

Give two examples of radiation from manmade sources.

Back 10

1) Nuclear fallout (from weapons tests, nuclear accidents or dumped nuclear tests).

2) Medical - x-rays, for example.

Front 11

What does the likelihood of suffering damage after being exposed to radiation depend on?

Back 11

The radiation dose.

Front 12

What does radiation dose depend on?

Back 12

The type and amount of radiation you've been exposed to (which is affected by location and occupation).

Front 13

Complete this sentence:

The higher the radiation dose...

Back 13

...the more at risk you are of developing cancer.

Front 14

How do underground rocks affect a person's dose of radiation?

Back 14

Underground rocks (like granite) can cause higher levels at the surface, especially if they release radioactive radon gas, which can get trapped inside people's houses.

Front 15

At high altitudes, background radiation increases. Why?

Back 15

At high altitudes, your exposure to cosmic rays is higher.

Front 16

Give four examples of occupations which may have a increased risk of cancer.

Back 16

1) Pilots - increased exposure to cosmic rays.

2) Underground miners - there are rocks around everywhere.

3) Nuclear industry workers and uranium miners - exposed to 10 times the normal amount of radiation.

4) Radiographers - they use ionising radiation and have a higher risk of radiation exposure.

Front 17

What do nuclear industry workers and uranium miners wear to protect themselves?

Back 17

Protective clothing and face masks to stop them from touching or inhaling the radioactive material. They monitor their radiation doses with special radiation badges and regular check-ups.

Front 18

What do radiographers do to limit their radiation exposure?

Back 18

They wear lead aprons and stand behind lead screens to protect them from prolonged exposure to radiation.

Front 19

What is an alpha particle composed of?

Back 19

Two neutrons and two protons - the same as a helium nucleus. It has a positive charge.

Front 20

True or false:

Alpha particles don't travel very far, even through air.

Back 20

True. Alpha particles are relatively big and heavy and slow moving - therefore they don't penetrate very far into materials and are stopped quickly.

Front 21

Alpha particles are described as strongly ionising. Why?

Back 21

Because of their size, alpha particles are described as 'strongly ionising' - they collide with a lot of atoms and knock electrons off them before they slow down, which creates lots of ionising.

Front 22

What 'ionising radiation'?

Back 22

Radiation that creates ions of atoms.

Front 23

What are beta particles?

Back 23

Electrons.

Front 24

True or false:

In terms of their properties, beta particles are in between alpha and gamma.

Back 24

True. Beta particles move quite fast and they're quite small.

Front 25

How far do beta particles penetrate into materials?

Back 25

Beta particles penetrate moderately into materials before stopping. They have a long range in air and are moderately ionising too.

Front 26

For every beta particle emitted, what happens?

Back 26

A neutron turns into a proton and an electron and the electron is emitted.

Front 27

What is:

a) The mass

b) The charge

Of a beta particle?

Back 27

a) Virtually nothing (0.005 relative mass)

b) A charge of -1

Front 28

What are gamma rays?

Back 28

Very short wavelength electromagnetic waves.

Front 29

Comparatively, how far do gamma rays penetrate into materials?

Back 29

Gamma rays penetrate the deepest into materials (when compared with the other types of radiation) and pass straight through air.

Front 30

Gamma rays are weakly ionising. Why?

Back 30

They pass through rather than collide with atoms. Eventually they do collide with something and do damage.

Front 31

What is:

a) The mass

b) The charge

of gamma rays?

Back 31

a) Nothing

b) No charge

Front 32

True or false:

All types of radiation are deflected by electric and magnetic fields.

Back 32

False.

Gamma radiation is an EM wave and has no charge, so it doesn't get deflected by electric or magnetic fields.

Front 33

When travelling through a magnetic or electric field, what happens to alpha and beta particles? Why?

Back 33

Both alpha and beta particles will be deflected in opposite directions because of their opposite charges.

Front 34

Why do alpha particles feel a greater force in magnetic and electric fields?

Back 34

Because alpha particles have a larger charge than beta particles.

However, because they have a much greater mass, they're deflected less.

Front 35

What is the unit used for measuring radioactivity?

Back 35

The becquerel (Bq)

1 Bq means one nucleus decaying per second.

Front 36

True or false:

The radioactivity of a sample always decreases over time.

Back 36

True. Each time a decay happens and an alpha, beta or gamma is given out, it means one more radioactive nucleus has disappeared.

Front 37

Complete this sentence:

As the unstable nuclei disappear...

Back 37

...the activity will decrease.

The older a sample becomes, the less radiation it will emit.

Front 38

What is the problem with trying to measure how quickly all of the unstable nuclei in a sample will decay?

Back 38

The activity never reaches zero.

Front 39

What is half-life?

Back 39

The average time it takes for the number of nuclei in a radioactive isotope sample to halve.

The time it takes for the count rate from a sample containing the isotope to fall to half its initial level.

Front 40

What does a short half-life mean?

Back 40

The activity falls quickly because lots of the nuclei decay quickly.

Front 41

What does a long half-life mean?

Back 41

The activity falls more slowly because most of the nuclei don't decay for a long time.

Front 42

State four uses of radiation.

Back 42

1) Smoke detectors

2) Tracers in medicine

3) Radiotherapy

4) Sterilisation of food

Front 43

Describe the use of radiation in smoke detectors.

Back 43

1) A weak source of alpha radiation is placed in the detector, close to two electrodes.

2) The source causes ionisation and a current flows between the electrodes.

3) If there is a fire then smoke will absorb the radiation - the current stops and the alarm sounds.

Front 44

What type of radiation is used in tracers in medicine?

Back 44

Gamma or beta emitters - NEVER alpha - so that radiation passes out of the body.

Front 45

What should the length of the half life of a radioactive isotope used as a tracer in medicine be?

Back 45

A short half-life - so that the radiation inside the patient disappears quickly.

Front 46

How are radioactive isotopes (medical tracers) put into patients?

Back 46

Certain radioactive isotopes can be injected into people (or they can be swallowed).

Their progress around the body can be followed using an external detector. A computer converts the reading to a display showing where the strongest reading is coming from.

Front 47

Give an example of a tracer used in medicine.

Back 47

Iodine-131. It is absorbed by the thyroid gland but gives out radiation which can be detected to indicate whether the thyroid gland is taking in iodine as it should.

Front 48

Describe how radiation is used in radiotherapy.

Back 48

Since high doses of gamma rays will kill all living cells, they can be used to treat cancers.

The gamma rays have to be directed carefully at just the right dosage to kill the cancer cells without damaging too many normal cells.

Front 49

Give one disadvantage of using radiotherapy to treat cancer.

Back 49

Gamma rays still cause a large amount of damage to normal cells, which makes the patient feel very ill.

However, if the cancer is eliminated, this is worth it.

Front 50

Describe how radiation can be used to sterilise food and surgical instruments.

Back 50

Food can be exposed to a high dose of gamma rays which will kill all microbes, keeping the food fresh for longer.

Medical instruments can be sterilised in the same way.

Front 51

Give an advantage of using irradiation over boiling to sterilise something.

Back 51

It doesn't involve high temperatures, so things like fresh apples or plastic instruments can be sterilised without damaging them.

Front 52

True or false:

Food or medical instruments sterilised with gamma rays will be radioactive afterwards.

Back 52

False. These items will not become radioactive - the food is perfectly safe to eat and the medical instruments are perfectly safe to use.

Front 53

Describe the type of isotope needed (in terms of half-life) for irradiation purposes.

Back 53

It must be a very strong emitter of gamma rays with a reasonably long half-life (at least several months) so that it won't need replacing too often.

Front 54

What is irradiation?

Back 54

The process by which an object is exposed to radiation; the sterilisation of food and surgical instruments using gamma rays.

Front 55

How and why does alpha, beta and gamma radiation cause damage to living cells.

Back 55

The radiation enters living cells, colliding with molecules. These collisions cause ionisation, which damages or destroys the molecules.

Front 56

True or false:

Lower doses of radiation tend to cause minor damage without killing the cell.

Back 56

True.

Front 57

What can low doses of radiation lead to?

Back 57

Mutant cells which divide uncontrollably (cancer).

Front 58

What does the extent of the harmful effects depend on?

Back 58

1) How much exposure you have to the radiation.

2) The energy and penetration of the radiation, since some types are more hazardous than others.

Front 59

When you are exposed to a high dose of radiation?

Back 59

Body cells exposed may be killed completely. This causes radiation sickness if a lot of cells are killed at once.

Front 60

Which two sources are most dangerous outside of the body? Why?

Back 60

Beta and gamma sources are the most dangerous because these types can get inside the body and penetrate the delicate organs.

Front 61

Outside the body, why is alpha radiation much less dangerous?

Back 61

It cannot penetrate the skin.

Front 62

Inside the body, which source of radiation is the most dangerous?

Back 62

Alpha sources do the most harm inside the body - they cause damage in a very localised area.

Front 63

Inside the body, why is gamma and beta radiation less dangerous?

Back 63

They pass straight out of the body without causing much damage.

Front 64

State 6 precautions taken when handling radioactive materials.

Back 64

1) The source is used for as short a time as possible, keeping exposure to the minimum.

2) The source is handled with tongs.

3) The source is held at arm's length to keep it far from the body.

4) The source is kept pointing away from the body and one must avoid looking at it.

5) Store radioactive substances in a lead box.

6) In medicine, only the area that needs to be treated is exposed to radiation.

Front 65

What is nuclear fission?

Back 65

The splitting up of big atomic nuclei.

Front 66

What do nuclear power stations use to generate electricity?

Back 66

Nuclear reactors.

Front 67

What happens in a nuclear reactor?

Back 67

A controlled chain reaction takes place in which atomic nuclei split up and release energy in the form of heat.

Front 68

What is the heat released after an atomic nuclei splits up used for?

Back 68

The heat released is simply used to heat water to make steam which is used to drive a steam turbine connected to an electricity generator.

Front 69

Which elements are normally used in nuclear fission?

Back 69

Uranium-235 or plutonium-239 (or both).

Front 70

Describe what must happen to start the chain reaction in the nuclear reaction.

Back 70

A slow moving neutron is absorbed into the uranium or plutonium nucleus. This addition of a neutron makes the nucleus unstable, which causes it to split.

Front 71

What happens each time a uranium or plutonium nucleus splits up?

Back 71

It spits out two or three neutrons. One of which might hit another nucleus, causing it to split also, thus keeping the chain reaction going.

Front 72

When a large atom splits in two, what does it form?

Back 72

Two smaller nuclei are formed. They're normally reactive because they have the 'wrong' number of neutrons in them.

Front 73

What is a nucleus splitting called?

Back 73

A fission.

Front 74

True or false:
A fission gives out a lot of energy - lots more energy than you get from any chemical reaction.

Back 74

True.
Nuclear processes release much more energy than chemical processes do.

Front 75

Why are nuclear bombs so much more powerful than ordinary bombs?

Back 75

Ordinary bombs rely on chemical reactions, which release a lot less energy than nuclear reactions.

Front 76

What is the main problem with nuclear power?

Back 76

The disposal of waste. The products left over after nuclear fission are highly radioactive so they can't just be thrown away. They're very difficult and expensive to dispose of safely.

Front 77

Nuclear fuel is cheap, but the overall cost of nuclear power is high. Explain why.

Back 77

The cost of the power plant is high and the overall cost has to take into account the cost of decommissioning the power plant (which takes decades).

Front 78

Give two risks of nuclear power.

Back 78

1) Radiation leaks.

2) There could be a major catastrophe (like Chernobyl).

Front 79

What is nuclear fusion?

Back 79

The joining of small atomic nuclei. Two light nuclei (like hydrogen) can join to create a larger nucleus.

Front 80

True or false:
Fusion doesn't release a lot of energy - less than fission.

Back 80

False.
Fusion releases lots of energy - more than fission for a given mass.

Front 81

Where does the energy released in stars come from?

Back 81

Nuclear fusion.

Front 82

Give some advantages of using fusion over fission to generate electricity.

Back 82

Fusion doesn't leave behind a lot of radioactive waste like fission. Left over hydrogen can also be used as fuel.

Front 83

What are some problems with using fusion to generate electricity?

Back 83

1) It can only happen at really high temperatures - about 10,000,000 degrees Celsius.

2) You can't hold hydrogen at the high temperatures and pressures required for fusion in an ordinary container - you need an extremely strong magnetic field.

3) At the moment it takes more power to create the conditions for fusion than we can get out of it.

Front 84

Name the stages of the life cycle of a star that's much bigger than the sun.

Back 84

1) Protostar

2) Main sequence star

3) Red super giant

4) Supernova

5) Neutron star

OR

5) Black hole

Front 85

Name the stages of the life cycle of a star that's about the same size as the sun.

Back 85

1) Protostar

2) Main sequence star

3) Red giant

4) White dwarf

5) Black dwarf.

Front 86

Describe the first stage in a star's life cycle - the protostar.

Back 86

The star initially forms from clouds of dust and gas. The force of gravity makes the gas and dust spiral in together to form a protostar.

Front 87

Describe what happens to the protostar for it to become the main sequence star.

Back 87

1) Gravitational energy is converted into heat energy, so the temperature rises.

2) When the temperature gets high enough, hydrogen nuclei undergo nuclear fusion to form helium nuclei and give out massive amounts of heat and light.

3) A star is born.

Front 88

When a star is born, what pull together to make planets that orbit it?

Back 88

Smaller masses of gas and dust pull together to make planets that orbit the star.

Front 89

Describe the long stable period (when it's called a main sequence star) that the star undergoes.

Back 89

1) The heat created by the nuclear fusion provides an outward pressure to balance the force of gravity pulling everything inwards.

2) The star maintains its energy output for millions of years due to the massive amounts of hydrogen it consumes.

Front 90

Approximately how long does the stable period last?

Back 90

Several billion years.

Front 91

What happens to cause a star to become a red giant (or a red super giant)?

Back 91

1) The hydrogen begins to run out. Heavier elements like iron are made by nuclear fusion of helium.

2) The star then swells into a red giant if it's a small star, or a red super giant if it's a big star.

Front 92

Why is a red giant (or a red super giant) red?

Back 92

The surface cools.

Front 93

What happens when a small-to-medium sized star (like the sun) becomes unstable?

Back 93

It ejects its outer layer of dust and gas as a planetary nebula.

Front 94

When a small-to-medium sized star ejects its outer layer of dust and gas, what does it leave behind?

Back 94

A hot, dense solid core - a white dwarf.

Front 95

When a white dwarf cools, what does it become?

Back 95

A black dwarf. It eventually disappear.

Front 96

After a big star becomes a red super giant, what happens?

Back 96

1) It starts to glow brightly again as it undergoes more fusion and expands and contracts several times.

2) Elements as heavy as iron are formed in various nuclear reactions.

3) Eventually it explodes in a supernova, forming elements heavier than iron and ejecting them into the universe to form new planets and stars.

Front 97

When an exploding supernova throws the outer layers of dust and gas into space, what does this leave?
If it's big enough, what will it become?

Back 97

A very dense core called a neutron star.
If this star is big enough, this will become a black hole.