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Science '23 > Nuclear Physics > Flashcards

Nuclear Physics Flashcards

1
Q

Atomic Number

A

Number of protons in the nucleus

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2
Q

Atomic Mass

A

Proton number + neutron number

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3
Q

Protons

A

Subatomic particles found in the atomic nucleus that carry a positive charge.

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4
Q

Neutrons

A

Subatomic particles found in the atomic nucleus that carry no charge but contribute to the mass of the atom.

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5
Q

Nucleon

A

The name given to the particles of the nucleus (protons and neutrons).

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6
Q

Strong Nuclear Force

A

The force that holds nuclei (nucleons) together and is responsible for binding together quarks. It is the strongest of the four fundamental forces.

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7
Q

Electromagnetic Force

A

The interaction between charged particles, causing attraction between opposite charges and repulsion between like charges.

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8
Q

Isotope

A

Nuclei with the same number of protons but different number of neutrons.

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9
Q

Binding energy

A

The energy required to hold the constituents parts together as a nucleus.

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10
Q

Radioactive decay

A

A natural process in which the nucleus of an unstable atom transforms by emitting particles (e.g. alpha or beta particles) or electromagnetic radiation (e.g. gamma rays).

This transformation occurs in order to achieve a more balanced and stable configuration.

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11
Q

Relate knowledge of strong nuclear force and (counters) electromagnetic force to the stability of nucleus.

A

For the nucleus to be stable, the strong nuclear force needs to be stronger than the electromagnetic force, holding the nucleus together.

When it becomes unbalanced, and the electromagnetic force overcomes the strong nuclear force, nuclei can become unstable and undergo processes like radioactive decay.

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12
Q

Alpha decay

A

Too much mass in the atom leads to an unstable nucleus. The atom emits an alpha particle (two protons and two neutrons) to become more stable
- The atomic nucleus loses two protons and two neutrons, resulting in a decrease in the atomic number (Z) by 2 and the mass number (A) by 4
- This emission of the alpha particle from the nucleus reduces its size and stabilises it.

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13
Q

Alpha particle

A

A type of subatomic particle that consists of two protons and two neutrons (essentially equivalent to the nucleus of a helium-4 atom.)

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14
Q

Alpha particle mass

A
  • Heavy
  • 4 atomic mass units
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15
Q

Alpha particle charge

A

Positive charge of +2e

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16
Q

Alpha particle speed

A

Slow (velocity is <0.1c) – c is speed of light in a vacuum.

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17
Q

Alpha particle penetrating ability

A

Low penetrating ability
Can penetrate <2cm of air

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18
Q

Alpha particle ionising abillity

A
  • High
  • Highly ionising over very short distances (because high ionisation and low penetration)
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19
Q

Do alpha particles have great potential to do biological harm?

A

Can cause biological harm by ionising cells and damaging DNA if ingested. However, due to the limited penetrating ability, it can be stopped easily by skin, and therefore it will only cause harm if ingested. (Highly ionising over short distances)

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20
Q

Alpha decay energy release

A
  • Alpha decay releases a significant amount of kinetic energy carried by the emitted alpha particle.
  • The energy is a result of the binding energy, which holds the protons and neutrons together in the nucleus, being released when the alpha particle is emitted.
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21
Q

Relate nucleus size to stability

A
  • In atoms where nuclei are small, the Strong Nuclear force overpowers the electrostatic force.
  • As the nucleus gets bigger (elements with a higher number of nucleons), the electrostatic force becomes greater than the strong nuclear force.
  • These nuclei are called unstable as they are able to eject particles and energy in order to return to a stable state. It is referred to as radiation and the atom is said to be radioactive.
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22
Q

Radiation

Define and state how it travels

A

The transfer of energy through space from a source. It travels through space as particles or waves.

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23
Q

What can alpha particles be stopped by?

A

Paper

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24
Q

Beta decay

A

When there are too many neutrons in a nucleus a neutron is changed into a proton and an electron, making a more stable nucleus.
- The new proton = positively charged = positron
- The new electron = negatively charged = negatron

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25
Q

What happens to the new electron and new proton during beta decay?

A
  • The newly created electron (negatron) shoots out of the nucleus at 98% the speed of light i.e. very fast
  • The positron remains in the nucleus
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26
Q

What is the beta particle in beta decay?

A

The newly created electron (negatron) that shoots out of the nucleus.

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27
Q

What happens to the newly created proton (positron) during beta decay?

A

It remains in the nucleus

28
Q

Beta particle mass

A
  • Very light
  • (1/2000 atomic mass units)
29
Q

Beta particle speed

A

Very fast. 98% of speed of light (0.98c)

30
Q

Beta particle ionising ability

A

Medium

31
Q

Beta particle penetrating power

A
  • Medium
  • Can travel through many cm or even meters of air, a few mm of skin
32
Q

What are beta particles stopped by?

A

Aluminium or perspex

33
Q

Gamma radiation

A

An excited nucleus is unstable and releases a gamma ray to obtain stability

34
Q

Electromagnetic radiation

A

Stream of photons that are massless particles travelling in wave-like pattern

35
Q

Gamma rays

A

High-energy electromagnetic radiations (EMR) emitted from the nucleus

36
Q

Gamma ray mass

A

No mass as it is radiation

37
Q

Gamma ray speed

A

Speed of light

38
Q

Gamma ray ionising ability

A
  • Low
  • Gamma rays do not directly ionise other atoms, but they may cause atoms to emit other particles which will then cause ionisation.
39
Q

Gamma ray penetrating power

A

High

40
Q

What can gamma rays be stopped by?

A

Lead

41
Q

Ionising radiation

A
  • A type of energy that can take electrons from atoms, creating charged particles.
  • Can harm living cells and is used in medical procedures like X-rays.
42
Q

Examples of ionising radiation

A
  • Alpha particles
  • Beta particles
  • Gamma particles
43
Q

Examples of non ionising radiation

A
  • Radio waves
  • Microwaves
  • Infrared radiation
44
Q

How does a nucleus become unstable? What does this cause it to do?

A

When the electrostatic force is greater than the strong nuclear force that holds the nucleus together.

This causes it to go through radioactive decay.

45
Q

Mass Defect (Δm)

A

The difference between the mass of the atom and the sum of the masses of its parts.

46
Q

Define

Fusion

A

A nuclear reaction in which two or more light atomic nuclei combine to form one or more different, heavier atomic nuclei and subatomic particles

47
Q

What is the mass defect in fusion?

A

The mass defect is the binding energy that is released, since the nucleus that is formed is more stable

48
Q

Define

Fission

What does it form/release?

A

A nuclear reaction in which a large unstable nucleus splits, forming/releasing:
- Two (or more) smaller, more stable nuclei
- Fast neutrons
- Energy in the form of heat

  • A large, unstable atom absorbs a slow neutron, which causes it to split into two smaller nuclei.
  • These two fission fragments are much more stable than the original nucleus
49
Q

Describe:

Fission chain reaction

A
  • Each released fast neutron can itself induce fission releasing more energy
  • The next fission reaction also creates neutrons that can again cause fission releasing more energy
  • A chain reaction is created that releases a lot of energy
50
Q

Uncontrolled vs controlled chain reaction

Describe how it is controlled

A
  • Uncontrolled reactions are used in nuclear bombs because they magnify the original effect
  • Controlled reactions are used in nuclear power plants because they sustain the original effect
  • Neutrons released from the fission reaction are absorbed and won’t cause more fission (controlled)
51
Q

Mass defect and binding energy in fission

A
  • The mass of the fission fragments is always less than the mass of the original particles
  • This mass defect is equivalent to the energy that is released during each fission
52
Q

Relationship between nuclear stability/size and fission/fusion.

Also discuss binding energy

A
  • Nuclei with a large binding energy per nucleon are most stable.
  • Smaller nuclei will undergo fusion to become more stable.
  • Larger nuclei will undergo fission to become more stable.
53
Q

Describe the relationship between mass and energy using E = mc^2.

A

It shows how mass (m) can be converted into energy (E).
- Even a small amount of mass contains a large amount of energy.
- When mass is converted into energy, it can release a large amount of energy (the basis for nuclear reactions, the atomic bomb, and nuclear power plants)
- (Also, energy can condense into mass under extreme conditions, such as within black holes.)

54
Q

Define:

Half-life

A

The time it takes for half of a radioactive substance to decay/ transform into a more stable form.

55
Q

Main components of a nuclear power station

A
  • Reactor vessel
  • Control rods
  • Fuel rods
  • Steam generator
  • Moderator
55
Q

Reactor vessel

Nuclear power station

A

Encases and prevents radiation from escaping

55
Q

Fuel rods

Nuclear power station

A
55
Q

Control rods

Nuclear power station

A

Function in controlling nuclear reactions by absorbing neutrons to prevent further fission.

55
Q

Steam generator

Nuclear power station. Has three parts.

A
56
Q

Explain, simply, how a nuclear power station works.

A

A nuclear reactor is a device in which nuclear reactions are generated, and the chain reaction is controlled to release a large amount of steady heat, thereby producing energy.

56
Q

Moderator

Nuclear power station. + Give examples.

A

Slows neutrons to allow fission to occur. E.g. graphite, heavy water.

57
Q

Uncontrolled nuclear reaction

A

Neutrons escape too quickly to maintain a chain reaction, resulting in the rapid release of nuclear energy, causing an explosion.

58
Q

Controlled nuclear reaction

A
59
Q

Advantages of nuclear power

A
60
Q

Disadvantages of nuclear power

A
61
Q
A

Science '23 (5 decks)

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