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iGCSE Physics > Radioactive Decay > Flashcards

Radioactive Decay Flashcards

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1
Q

What is the atomic number of the nucleus shown below?

A

3 (this lower number is also known as the ‘proton number’)

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2
Q

What is the mass number of the nucleus shown below?

A

7 (this upper number is also known as the ‘nucleon number’)

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3
Q

What is the nucleon number of the atom shown below?

A

7 (this upper number is also known as the ‘mass number’)

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4
Q

What is the proton number of the atom shown below?

A

3 (this lower number is also known as the ‘atomic number’)

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5
Q

How many protons does the nucleus shown below have?

A

3

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6
Q

How many neutrons does the nucleus shown below have?

A

4 (it’s the difference between the mass number and the proton number)

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7
Q

Lithium-6 and Lithium-7 are isotopes. What does the word ‘isotopes’ mean here?

A

It means they have the same number of protons but different numbers of neutrons

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8
Q

What is the mass number of Lithium-7?

A

7

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9
Q

Sometimes a large, unstable nucleus will change into a new element, emitting an energetic particle as it does so. What is the name for this process?

A

Radioactive decay

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10
Q

During alpha decay, an unstable nucleus emits an alpha particle. What is an alpha particle?

A

A highly energetic particle made of two protons and two neutrons

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11
Q

During beta decay, an unstable nucleus emits an alpha particle. What is a beta particle?

A

A very high energy electron

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12
Q

What is a gamma ray?

A

A very high frequency electromagnetic wave

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13
Q

We refer to alpha particles, beta particles and gamma rays as ‘ionising radiation’. What does this mean?

A

They can knock electrons off atoms (when they collide with them)

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14
Q

Which kind of ionising radiation can be stopped by a sheet of card?

A

Alpha particles

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15
Q

Which kind of ionising radiation can be stopped by a few cm of air?

A

Alpha particles

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16
Q

Which kind of ionising radiation will pass through card, but can by stopped by a few mm of aluminium?

A

Beta particles

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17
Q

Which kind of ionising radiation will pass through a few mm of aluminium, but will be stopped by a few metres of lead?

A

Gamma rays

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18
Q

Name two things you could use to detect ionising radiation.

A

A Geiger counter
Photographic film

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19
Q

Name two health risks posed by exposure to ionising radiation.

A 
Cell damage
Genetic mutation (including a risk of cancer)
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20
Q

What is the name for the energetic particle made up of two protons and two neutrons, sometimes released when an unstable nucleus decays?

A

An alpha particle

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21
Q

What is the name for a highly energetic electron, sometimes released when an unstable nucleus decays?

A

A beta particle

22
Q

What is the name of the high frequency e-m wave emitted when an unstable nucleus decays?

A

A gamma ray

23
Q

What is the mass number of an alpha particle?

A

4

24
Q

What is the proton number of an alpha particle?

A

2

25
Q

What is the mass number of a beta particle?

A

0

26
Q

What is the proton number of a beta particle?

A

-1

27
Q

What number should replace the question mark in the nuclear decay equation shown below?

A

206 (the nucleon numbers to the left of the arrow must add to equal the nucleon numbers to the right of the arrow)

28
Q

What number should replace the question mark in the nuclear decay equation shown below?

A

85 (the proton numbers to the left of the arrow must add to equal the proton numbers to the right of the arrow)

29
Q

What number should replace the question mark in the nuclear decay equation shown below?

A

7 (the proton numbers to the left of the arrow must add to equal the proton numbers to the right of the arrow)

30
Q

What number should replace the question mark in the nuclear decay equation shown below?

A

14 (the mass numbers to the left of the arrow must add to equal the mass numbers to the right of the arrow)

31
Q

What is the name for the radiation all around us, that we are exposed to as a result of everyday life?

A

Background radiation

32
Q

Name three natural sources of background radiation.

A

Cosmic rays
Radon gas from rocks
Food and drink

33
Q

Name two artificial sources of background radiation

A

Medical x-rays
Nuclear power stations

34
Q

A nuclear reactor contains ‘fuel rods.’ What are ‘fuel rods’?

A

They are where the nuclear fission occurs. They contain the nuclear fuel.

35
Q

A nuclear reactor contains ‘control rods.’ What is the function of the ‘control rods’?

A

Control rods are made of boron and absorb neutrons. They can be raised and lowered between the fuel rods to increase or decrease the rate of the fission reaction.

36
Q

A nuclear reactor contains a ‘moderator.’ What is the role of the ‘moderator’?

A

A moderator is a chemical that slows down neutrons, making them more efficient at causing nuclear fission.

37
Q

“Nuclear fission can occur when a ……….. collides with an unstable nucleus.” What is the missing word?

A

neutron

38
Q

“A neutron can cause an unstable nucleus to undergo nuclear fission. The products of this reaction are a daughter nucleus, heat energy, and three or more ………….” What is the missing word?

A

neutrons

39
Q

“A neutron can cause an unstable nucleus to undergo nuclear fission. The products of this reaction are ……………., heat energy, and three or more neutrons.” What is the missing phrase?

A

a daughter nucleus

40
Q

What units is activity measured in?

A

Becquerels (Bq)

41
Q

What does an activity of 600 Bq mean?

A

600 unstable nuclei decay every second

42
Q

You measure the activity of a source. After 3 seconds your geiger counter has detected 600 decays. What is the activity of the source?

A

200 Bq (because there must be 200 decays every second)

43
Q

Explain what is meant by ‘the half-life of a radioactive sample’

A

The half life is the time taken for half of the atoms in a radioactive sample to decay
OR
The half life is the time taken for the activity of a radioactive sample to halve

44
Q

Sodium-24 has a half-life of 15 hours. What fraction of a sample of sodium-24 will remain after 45 hours?

A

An eighth. (In this case, 45 hours is three half-lives. So the sample will have halved three times. Half of a half of a half is an eighth)

45
Q

A sample of Iodine has an activity 1200 Bq and a half-life of 8 days. What will the activity of the source be after 16 days?

A

300 Bq. (In this case, 16 days is two half-lives. So the activity will have halved two times. Halve 1200 and then halve it again to get your answer)

46
Q

Bismuth-212 has a half-life of 60 seconds. A sample containing 800 atoms of Bismuth-212 is left for 4 minutes. How many atoms remain after this time?

A

50 atoms. (4 minutes = 4 half lives, in this case. So halve 800 four times to get your answer)

47
Q

Name four uses of radioactive sources

A

Smoke detectors
Medical tracers
Monitoring the thickness of paper in a paper mill
Carbon dating

48
Q

Which kind of source is used in smoke detectors (alpha, beta or gamma) and why?

A

Alpha.
Only alpha would be strongly absorbed by the smoke. Beta and gamma are too penetrating to be strongly absorbed by the smoke.

49
Q

Which kind of source (alpha, beta or gamma) is used to measure the thickness of paper in a paper mill and why?

A

Beta.
Alpha is not penetrating enough and would almost all be absorbed by the paper. Gamma is too penetrating and would hardly be absorbed at all.

50
Q

Isotope A has a half-life of 5 minutes. Isotope B has a half-life of 3 hours. Isotope C has a half-life of 16 years. Which isotope could a doctor use as a medical tracer, and why?

A

Only isotope B has a suitable half-life. The half-life of A is too short: little activity will remain by the time it is administered to the patient. The half-life of C is too long: it will continue to expose the patient to radiation long after they have left the hospital.

iGCSE Physics (10 decks)

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