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Physics > P4 - Atomic Structure > Flashcards

P4 - Atomic Structure Flashcards

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1
Q

State four types of nuclear radiation.

A

Alpha Particles
Beta Particles
Gamma rays
Neutrons

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2
Q

What is meant by background radiation?

A

Radiation that is always present. It is in very small amounts so is not harmful.

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3
Q

Give 4 sources of background radiation.

A

Nuclear weapon testing
Nuclear accidents
Rocks
Cosmic rays from space

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4
Q

How do you measure and detect background radiation?

A

Geiger Muller Tube
Photographic film

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5
Q

How does a Photographic film detect radiation?

A

Turns darker when it is exposed to radiation.

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6
Q

How does a Geiger Muller tube measure background radiation?

A

When a Geiger Muller tube absorbs radiation is produces a pulse which a machine then uses to count the amount of radiation.

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7
Q

What constitutes an alpha particle?

A

Two protons and two neutrons.
Same as a helium nucleus.

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8
Q

What is the range of an alpha particle through air?

A

A few cm

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9
Q

What will block beta radiation?

A

Thin sheet of aluminium.
Several metres of air.

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10
Q

What will block gamma radiation?

A

Several cm of lead.
A few metres of concrete.

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11
Q

What type of radiation is the most ionising?

A

Alpha particle due to its large mass it has the highest ionising power and the greatest ability to damage tissue

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12
Q

What type of radiation is least ionising?

A

Gamma.

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13
Q

How does gamma emission effect the mass and charge of an atom?

A

Both mass and charge remained unchanged.

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14
Q

Prior to the discovery of an electron what was believed about the atom?

A

It was indivisible.

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15
Q

What experiment led to the plum pudding model being discarded?

A

Rutherfords alpha particle scattering experiment.

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16
Q

What are the conclusions of Rutherford’s experiment?

A

Most of the atom is empty space
The mass of the atom is concentrated at the nucleus
Nucleus has a positive charge

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17
Q

What happens in the process of beta plus decay?

A

A proton turns into a neutron and a positron in order to conserve charge.

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18
Q

What is the process called when a neutron turns into a proton and an electron?

A

Beta minus decay

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19
Q

When alpha decay occurs what happens to the atomic number and the mass number of an atom?

A

mass number decreases by 4
atomic number decreases by 2
A new element is made since the atomic number has changed

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20
Q

What effect does beta minus decay have on the mass number and atomic number of the atom?

A

Mass number stays the same as the total number of protons and neutrons hasn’t changed one has just turned into the other.
Atomic number increases as there is one more proton

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21
Q

Give two ways that an atoms electron arrangement can be changed.

A

Absorbing electromagnetic radiation
Emitting electromagnetic radiation

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22
Q

Why do unstable nuclei undergo radiation?

A

They undergo decay to become more stable.

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23
Q

What is radioactive decay?

A

When an unstable nucleus gives out radiation to become more stable.

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24
Q

What is count-rate?

A

The number of radioactive decays per second from a radioactive source.

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25
Q

Define the half-life of a radioactive material.

A

The time it takes for the number of unstable nuclei to halve.

26
Q

What is irradation?

A

Exposing a material to nuclear radiation.
Material does not become radioactive.

27
Q

What is radioactive contamination?

A

The presence of unwanted radioactive nuclei on a material.

28
Q

What do all forms of the same element have in common?

A

They all have the same number of protons (atomic number).

29
Q

What is an isotope of an atom?

A

An atom of an element with the same number of protons but a different number of neutrons.

30
Q

What did James Chadwick’s experiments prove?

A

The existence of neutrons.

31
Q

What is nuclear fission?

A

The splitting of large unstable nuclei to form smaller stable nuclei. Emission of spare neutrons.

32
Q

What needs to happen to induce fission?

A

Unstable nuclei must absorb a neurton.

33
Q

What is emitted in a fission reaction?

A

Gamma rays.
Two or three neutrons.
Energy.

34
Q

What is the consequence of an uncontrolled chain reaction?

A

Results in a high production of energy.
Can result in a nuclear explosion.

35
Q

What are the three main components in the core of a nuclear reactor?

A

Moderator
Fuel Rods
Control Rods

36
Q

What is the role of a moderator (graphite core) in a nuclear reactor?

A

To slow down the speed of neutrons so they are travelling at speeds where they can be absorbed by nuclei and cause fission.

37
Q

How is the chain reaction in fission kept under control in a nuclear reactor?

A

The rate of fission is controlled by moving the control rods up and down. The lower the rods are inserted the slower the rate of fission.

38
Q

What is nuclear fusion?

A

The joining of two nuclei to produce a heavier nuclei and release energy.

39
Q

Which releases more energy nuclear fission or nuclear fusion?

A

Nuclear fusion.

40
Q

Explain the difficulty in generating energy through nuclear fusion.

A

Fusion requires very high temperatures which in itself requires large amounts of energy.

41
Q

Explain why nuclear fusion is not a viable way to produce energy on Earth.

A

The energy used to raise the temperature is greater than the energy that nuclear fusion releases. Resulting in energy loss.

42
Q

How many Millisieverts equal 1 Sievert?

A

1000

43
Q

What is the unit to measure radiation dosage?

A

Sievert

44
Q

Why are isotopes with long-half lives particularly dangerous?

A

They remain radioactive for much longer periods of time.

45
Q

Explain the process of radiotherapy.

A

Gamma emitters direct gamma rays at the cancerous cells.
The cancerous cells absorb the radiation and are killed.

46
Q

How are medical tracers chosen?

A

They should have a short half-life.
They should decay into a stable isotope that can be excreted.
They should only release gamma radiation as it is the least ionising, meaning it can pass through body tissue without damaging it.

47
Q

Why are beta particles deflected much more than alpa particles, despite the fact that alpha particles have a greater charge?

A

Beta particles have more charge in relation to their mass than alpha particles do (they have a greater specific charge)

48
Q

What makes alpha decay strongly ionising?

A

It can easily knock electrons off when it comes into contact with them, due to its large mass and strong positive charge.

49
Q

What holds stable nuclei together?

A

A strong nuclear force which can hold positive protons and neutral neutrons together.

50
Q

What determines if a nuclei is unstable?

A

There are too many neutrons or too many protons which upset the nuclear forces.

51
Q

What are gamma rays?

A

Rays of electromagnetic radiation that are usually emitted after beta or alpha decay as a way of getting rid of any extra energy.

52
Q

When will a neutron emission occur?

A

When there are too many neutrons in a nucleus. It will just throw one out.

53
Q

Why are gamma rays weakly ionising?

A

They have no mass or charge so they can penetrate long distances through materials without colliding with any other atoms.

54
Q

What does a beta minus decay release?

A

A negatively charged beta particle (an electron)

55
Q

What does beta plus decay release?

A

A positively charged beta particle (a positron)

56
Q

When does gamma decay occur?

A

When a nucleus is in an excited state and has too much energy to be stable. Often happens after beta or alpha decay.

57
Q

What is emitted in gamma radiation?

A

Energy

58
Q

What are fuel rods?

A

Holds the uranium isotopes.

59
Q

Why does fusion have to happen quickly?

A

The fusion of the nuclei has to happen quickly so that the repulsion of the charges does not have time to stop it from happening.

60
Q

Why is a shorter half-life better?

A

Activity decreases quickly.
Risk of harm decreases quickly.

61
Q

How is energy released in fusion?

A

Two smaller nuclei fuse to join heavier nuclei.
Some mass is converted into energy.

62
Q

Why is it good for medical tracers to be highly penetrating?

A

So, they can be detected outside the body. It needs to be able to escape skin.

Physics (9 decks)

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