P7 - Radioactivity Flashcards

1
Q

What is the nucleon number?

A

Number of protons plus neutrons

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2
Q

What is the relative masses of a proton, neutron and electron?

A

Electron - 0.0005
Proton - 1
Neutron - 1

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3
Q

Is the proton number on the bottom or top on the periodic table symbol?

A

It is on the bottom and is always the smaller number

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4
Q

What is ionising radiation?

A

The radiation emitted from unstable nuclei, that when in contact with a neutral atom can dislodge an electron and make it an ion. Made up of alpha, beta and gamma radiation.

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5
Q

Describe dalton’s model of the atom.

A

-All matter is made up of small, indivisible spheres.
-atoms of the same element are the same size and weight.
-During chemical reactions atoms rearrange to form different substances.

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6
Q

Describe the plum pudding model.

A

Atoms are positively charged spheres, with negatively charged electrons embedded within, like plums in a pie.

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7
Q

Describe the gold foil experiment?

A

It involved bombarding a thin sheet of gold foil with alpha particles, surrounded by a material that flashed when in contact with the alpha material.

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8
Q

Who created the gold foil experiment?

A

Ernest Rutherford

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9
Q

What were the takeaways from the gold foil experiment?

A

-showed nucleus was very, very small
-showed atom was mostly empty space
-most of atoms mass in nucleus
-nucleus was positively charged

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10
Q

What does ionising mean?

A

How well it rips off electrons .

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11
Q

What is the unit for radioactivity?

A

Becquerells (Bq)

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12
Q

What is an alpha particle?

A

A helium nucleus

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13
Q

What is a beta particle?

A

A fast moving electron

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14
Q

What is a gamma particle?

A

A wave

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15
Q

What stops the different radioactive particles?

A

Alpha - skin/paper
Beta - thin aluminium
Gamma - thick lead

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16
Q

What is the difference between ionising power and penetrating power?

A

Ionising power is how ionising (dangerous) the particle is and penetrating power is how easily it passes through objects.

17
Q

how do you do an alpha decay equation?

A

unstable atom -> more stable atom ( minus ^4 and 2) + helium nucleus (^4 and 2)

18
Q

Practise a beta decay question

A
19
Q

Practise a gamma decay question

A
20
Q

What is background radiation?

A

Naturally things around us and people release some radiation. This is called background radiation.

21
Q

How do you work out the uncertain of the mean background count?

A

Uncertainty = range of readings / 2

22
Q

What equipment do you use to measure radioactive activity?

A

A Geiger counter

23
Q

What is half-life?

A

Either…
- the time taken for the count rate to halve
- or the time taken for half of the radioactive nuclei in a sample to decay.

24
Q

How can you calculate half-life?

A

Amount after N half lives = (1/2)^N x initial amount

25
Q

What is a radioactive tracer ?

A

A tracer contains a radioactive isotope that emits gamma radiation that can be detected from outside the body. We can use this to check that parts of the body are functioning correctly e.g. if a kidney is blocked.

26
Q

Why might you use radioactive iodine as a medical tracer?

A
  • as it has a half life of 8 hours so will be long enough to carry out experiment but also not too long that the patient will be at risk of ionisation.
  • emits gamma radiation which is easily detected outside the body
  • the daughter nuclei are stable so the radiation will stop once out of system.
27
Q

How does radiotherapy work?

A

It works by firing a narrow beam of highly ionising radiation at cancerous cells, to kill them off. To stop all surrounding cells being killed the beam is rotated to make sure the cancerous cells are killed but surrounding cells aren’t exposed long enough to be killed.

28
Q

What is nuclear fission?

A

A type of nuclear reaction that is used to release energy from large unstable atoms by splitting them into smaller atoms. This rarely happens spontaneously, usually the nucleus will absorb a neutron before it will split.

29
Q

Describe the process of nuclear fission?

A

1) a slow neutron is absorbed by a uranium-235 nucleus
2) the resulting nucleus of uranium-236 is unstable
3) the nucleus splits apart into 2 lighter nuclei( daughter nuclei), 3 neutrons and gamma radiation.
4) the process then happens again as the 3 neutrons then get absorbed by another uranium-235 nucleus.

30
Q

What type of reaction is nuclear fission?

A

A chain reaction

31
Q

Name the different pieces of equipment used to control the nuclear fission and what they do.

A
  • graphite moderator, slows down the released neutrons so they can be absorbed by the next atom
  • boron control rods, are raised or lowered to change speed of reaction. When these are lowered fully the reaction is stopped.
  • concrete shielding - prevents radiation escaping from the core.
  • hollow fuel rods, contain pellets of uranium fuel.
32
Q

Give 2 pros and 2 cons of nuclear power.

A

Pros
1) low greenhouse gas emissions
2) high energy density
Cons
1)radioactive waste
2)potential for accidents

33
Q

What is nuclear fusion ?

A

Nuclear fusion is a process in which two lighter nuclei combine to form a heavier nucleus, releasing a large amount of energy in the process.

34
Q

What are the major drawbacks of nuclear fusion?

A

-To start the reaction off the nuclear fuel must be heated up to around 150 million degrees
-keeping plasma contained is very hard.
-easily disrupted.