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Physics (3.3) > Nuclear Physics and Radioactivity > Flashcards

Nuclear Physics and Radioactivity Flashcards

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1
Q

What did scientists believe about the atom before 1897?

A

Democritus the Greek proposed atoms (‘indivisible’) are smallest unit of matter and compose the world around us.

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2
Q

What were the results of Rutherford’s gold foil experiment?

A

Rutherford asked his lab assistants Hans Geiger and Ernest Marden to fire alpha particles, which are positive, at gold foil that was one-two atoms thick. He expected all the particles to pass through.
Most went straight through — the atom is mostly empty space.
Some were deflected by angles between 20° and 90° — a positive nucleus must be at the centre.
1 in 8000 rebounded — the nucleus contains 99% of atom’s mass.

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3
Q

What is the modern structure of the atom?

A

The Rutherford-Bohr model. This has the nucleus at the centre, with the shells as gradually larger circles around it. The electrons are drawn as dots or crosses.
[NB: technically outdated. The modern version insinuates that it is impossible to know the exact location of electrons.]

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4
Q

What is the modern definition of an atom?

A

The smallest unit of matter that has the properties of a chemical element.

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5
Q

What are the relative charges of electrons, protons and neutrons? why are they used?

A

Since particles are infinitesimally small, they are measured relative to e/o.
Protons have a relative charge of +1.
Neutrons have a relative charge of 0.
Electrons have a relative charge of -1.

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6
Q

What are the relative masses of protons, electrons and neutrons? why are they used?

A

Since particles are infinitesimally small, they are measured relative to e/o.
Protons have a relative mass of 1.
Neutrons have a relative mass of 1.
Electrons have a relative mass of 1/1840.

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7
Q

What does
A\/
Z/\ (i.e. ‘X’)
mean?

A

It is atomic notation — a simple way to show the amount of particles in an element.

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8
Q

What is the ‘A’ in ‘AZX’?

A

The mass or nucleon number. It shows us the amount of particles in the nucleus (i.e. nucleons).
[NB: actually written like
A\/
Z/\
]

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9
Q

What is the ‘Z’ in ‘AZX’?

A 
The atomic or proton number. It shows us the amount of protons and electrons in the atom. There is the same amount of protons as electrons in an atom in order to make it neutral overall.
[NB: actually written like
A\/
Z/\
]
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10
Q

What is the ‘X’ in ‘AZX’?

A 
The element.
[NB: actually written like
A\/
Z/\
]
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11
Q

How is the amount of protons in an atom determined from ‘AZX’?

A

The atomic/proton number.

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12
Q

How is the amount of neutrons in an atom determined from ‘AZX’?

A

The mass/nucleon number minus the atomic/proton number will give the amount of neutrons.

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13
Q

How is the amount of electrons determined from ‘AZX’?

A

The atomic/proton number, because in order to be neutral an atom must have the same amount of protons as electrons.
[NB: in an ion, the ‘AZX’ will have a number (e.g. 3 or -2) beside the ‘X’. Take this number away from the ‘Z’ to get the amount of electrons, i.e. x - 3 or x - (-2)]

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14
Q

What is an isotope? how are they identified?

A

An atom of the same element that has the same number of protons but a different number of neutrons.

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15
Q

What is radiation?

A

The emission of a particle or wave from the nucleus of an unstable atom. Sometimes termed nuclear radiation.

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16
Q

What is the SI unit of radiation? what is its symbol?

A

Becquerel (Bq), named after the discoverer, Henri Becquerel.

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17
Q

From where does nuclear radiation come?

A

The nucleus of an unstable atom.

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18
Q

Is nuclear radiation safe or dangerous?

A

Most is dangerous; however, it is safe in very small quantities.

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19
Q

What are the kinds of nuclear radiation? how many are there?

A

Three kinds: alpha, beta and gamma.

[NB: these are represented by their Greek letters.]

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20
Q

What is background radiation?

A

Low-level radiation that occurs naturally in the environment.

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21
Q

What are some sources of background radiation?

A

Rocks, soil, food, drink, radon, cosmic rays, laptops, mobiles, atomic bombs (?!!), nuclear power plants.

22
Q

What are the properties of alpha radiation? how far can it travel in air? by what is it blocked? what are its associated dangers and uses?

A 
Particle.
Range in air: 3cm.
Two neutrons and two protons.
Blocked by a sheet of A4 paper.
Used in smoke detectors.
Can cause cancer.
Relative mass of 4.
23
Q

What are the properties of beta radiation? how far can it travel in air? by what is it blocked? what are its associated dangers and uses?

A 
Particle.
Range in air: 30cm.
1 quick electron.
Blocked by 3-5mm of aluminium.
Used for nuclear power.
Can cause cancer.
Relative mass of 1/1840.
24
Q

What are the properties of gamma radiation? how far can it travel in air? by what is it blocked? what are its associated dangers and uses?

A

Wave.
Range in air: >300cm.
1 photon (a small elementary ‘particle’ filled with energy, usually light).
Blocked by 10-12cm of lead or 1m of concrete.
Used for food sterilisation.
Can cause cancer.
Relative mass of…

25
Q

What are some procedures to minimise risks associated with nuclear radiation?

A

Shielding — protective suits, lead/paper/aluminium/concrete, etc.
Distance — stay in another room with a window into the test’s room, keep the sample as far away as possible when handling, etc.
Time — minimise the length of the experiment.
Decontaminate surfaces/yourself after the experiment.

26
Q

What is a Geiger counter?

A

G(eiger)-M(üller) tubes (etc.) are used around the world to detect radiation. Geiger invented the principle in 1908.
Named after Hans Geiger (Rutherfordian) and Walther Müller.

27
Q

What is an ‘adjusted activity’ reading on a Geiger counter?

A

Before measuring the radiation from a specific source, background radiation should be measured. This should be subtracted from the final reading for an adjusted, verifiable reading that is purely for the source.

28
Q

What are some advantages of generating electricity from fossil fuels?

A 
Easily stored until needed.
Use proven technology (safe, unavailability of nuclear fusion, etc.).
Easily transported.
Available at many locations.
Cheaper than nuclear.
29
Q

What are some disadvantages of generating electricity from fossil fuels?

A 
Emit large amount of SO2 and CO2 (global warming, acid rain, changing climate, etc.).
Mining destroys habitats.
Non-renewable.
Available at many locations.
Cheaper than nuclear.
30
Q

How many stages are there to generating electricity in a power plant? what are they?

A

Three.
Use the energy in a fuel to heat water to produce steam.
Use the kinetic steam energy to spin a turbine.
Use the energy in the turbine to spin a generator and produce electricity.

31
Q

What is nuclear fission?

A

A heavy/large/massive nucleus (e.g. uranium-235) is split into two lighter nuclei by a slow neutron. This unstable process also releases heat energy and 2-3 more neutrons than can cause more fission (i.e. a chain reaction).

32
Q

Is nuclear fission natural or unnatural?

A

Unnatural — certain useful isotopes can be mined, enriched, concentrated and placed in a power plant and forced to do it.

33
Q

How much energy does nuclear fission produce relative to that of fossil fuels?

A

It produces four million times more energy per kg than fossil fuels.

34
Q

How is a nuclear power plant controlled?

A

In simple terms, the question ‘Generate more electricity?’ is asked.
If yes, the boron control rods (which control the rate of reaction) inside the fission reactor are raised to increase fission reaction.
If no, vice versa — lowered to decrease reaction.

35
Q

What are the parts of a fission reactor?

A

Refer to physical flashcard.

36
Q

What is nuclear fusion?

A

Two light hydrogen nuclei are joined/fused together to make a heavier helium nucleus, releasing energy and (a) neutron(s) in the process.

37
Q

Is nuclear fusion natural or unnatural?

A

Natural — gravitational fusion is how energy is generated in stars. All the elements of the periodic table can be created with fusion.

38
Q

How common is artificial nuclear fusion?

A

Exceedingly rare.

39
Q

What are some examples of nuclear fusion reactors?

A

Stars (gravitational), laser chambers (inertial) and tokamaks (magnetic).

40
Q

What are some challenges that the scientific community face in building a nuclear fusion reactor?

A

It calls for extraordinarily high temperatures and pressures. The hydrogen exists as a plasma — few containers can hold it as they would be destroyed.
It is costly and expensive.
It is a loss — more energy goes in than out.

41
Q

How and when was the electron discovered?

A

In 1897 — Joseph John Thompson conducts an experiment with electrically charged plates and discovers a tiny particle which he calls the electron.

42
Q

How and when was the nucleus discovered?

A

1909 through Rutherford’s gold foil experiment.

43
Q

How and when was the proton discovered?

A

Between 1919 and 1932, Rutherford proposed that a positive particle which he calls the proton is fundamental to understanding matter and is located inside the nucleus. It was discovered in 1898 by Wilhelm Wein.

44
Q

How and when was the neutron discovered?

A

In 1932. James Chadwick (a student of Rutherford) discovers a neutral particle in the nucleus. This proves a widely suspected theory about the atom’s centre.

45
Q

Where is radiation found?

A

Everywhere is small quantities. It is found in large amounts in nuclear reactions, reactors and power plants.

46
Q

What are some advantages of nuclear fission?

A

No greenhouse gasses (no global warming/acid rain/climate change/etc.).
Generates four million times more energy per kg than fossil fuels.

47
Q

What are some disadvantages of nuclear fission?

A

Waste is radioactive (and therefore toxic) for millions of years.
More expensive than generating electricity by fossil fuels.

48
Q

What are some advantages of nuclear fusion?

A

No dangerous waste.

No greenhouse gasses (no acid rain/global warming/climate change/etc.).

49
Q

What are some disadvantages of nuclear fusion?

A

Expensive and a loss of money as more energy goes in than out.
Few containers can hold it.

50
Q

How is nuclear radiation random?

A

It cannot be predicted.

51
Q

How is nuclear radiation spontaneous?

A

It happens w/o warning.

Physics (3.3) (3 decks)

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