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physics > topic 4 - atomic structure: atoms and nuclear radiation > Flashcards

topic 4 - atomic structure: atoms and nuclear radiation Flashcards

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1
Q

What happens with the nucleus of an atom when it tries to become more stable?

A

It gives out radiation in a process called radioactive decay.

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2
Q

What is radioactive decay?

A

A random process in which a nucleus gives out atomic radiation to become more stable?

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3
Q

Do stable or unstable atoms give out radioactive decay?

A

Unstable atoms.

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4
Q

What is activity?

A

The rate at which a source of unstable nuclei decays.

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5
Q

What is activity measured in?

A

Becquerel (Bq).

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6
Q

What is count rate?

A

The number of decays recorded each second by a detector.

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7
Q

Give an example of a detector used to measure count rate.

A

A Geiger-Muller tube.

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8
Q

What are the 4 types of ionising radiation which can be released from a nucleus?

A
  • Alpha
  • Beta
  • Gamma
  • Neutron
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9
Q

What is ionising radiation?

A

Radiation which knocks electrons off atoms.

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10
Q

What does ionising radiation create.

A

Positively charged ions.

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11
Q

What does the ‘ionising power’ of a radiation source mean?

A

How easily is can perform ionising radiation.

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12
Q

What is the symbol for an alpha particle/

A

α

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13
Q

What are alpha particles made up of?

A

2 protons and 2 neutrons.

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14
Q

What element has the same nucleus as an alpha particle?

A

Helium.

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15
Q

What is the penetration through materials of alpha particles like?

A

Don’t penetrate very far into materials and are stopped quickly - they are absorbed into a sheet of paper.

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16
Q

What is the range of alpha particles in air?

A

A few cm.

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17
Q

What is the ionising power of alpha particles like?

A

Strongly ionising.

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18
Q

Give a practical use of alpha particles.

A

Smoke detectors

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19
Q

How do alpha particles work in smoke detectors?

A

Smoke detectors ionise air particles, causing a current to flow. If there is smoke in the air, it binds to the ions, meaning the current stops and the alarm sounds.

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20
Q

What is the symbol for a beta particle?

A

β

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21
Q

What is a beta particle made up of?

A

A high-speed electron ejected from the nucleus as a neutron turns into a proton.

22
Q

What is the mass of a beta particle?

A

Virtually none.

23
Q

What is the charge of a beta particle?

A

-1

24
Q

What is the penetration through materials of beta particles like?

A

They penetrate moderately far before colliding.

25
Q

What is the range of beta particles in air?

A

A few metres.

26
Q

What material can be used to absorb beta particles?

A

A sheet of aluminium.

27
Q

How ionising are beta particles?

A

Moderately ionising.

28
Q

Give a use of beta particles.

A

Testing the thickness of sheets of metal.

29
Q

What is the symbol for gamma rays?

A

γ

30
Q

What is a gamma ray made up of?

A

Electromagnetic radiation from the nucleus.

31
Q

What is the pentration through materials of gamma rays like?

A

Penetrate far into materials without being stopped.

32
Q

How far can gamma particles travel through air?

A

A long distance.

33
Q

How ionising are gamma particles?

A

Weakly ionising.

34
Q

What can gamma particles be absorbed by?

A

Thick sheets of lead or metres of concrete.

35
Q

What are nuclear equations used to represent?

A

Radioactive decay.

36
Q

In nuclear equations, what symbol may an alpha particle be represented by?

A

He (mass no.=4, atomic no.=2)

37
Q

In nuclear equations, what symbol may a beta particle be represented by?

A

e (mass no.=0, atomic no.=-1)

38
Q

What is the general form of a nuclear equation?

A

atom before decay –> atom after decay + radiation emitted

39
Q

What must be equal on both sides of a nuclear equation?

A

The total mass and atomic numbers.

40
Q

How does alpha decay change the charge and mass of the nucleus?

A

It decreases both the charge and mass.

41
Q

How does beta decay affect the charge of a nucleus?

A

It increases the charge.

42
Q

How does the emission of a gamma ray affect the mass and charge of a nucleus?

A

It doesn’t affect it.

43
Q

Is radioactive decay predictable or random?

A

Random.

44
Q

What is the half life of a radioactive isotope?

A

The time it takes for the number of nuclei in a sample of the isotope to halve.
OR
The time it takes for the count rate from a sample containing the isotope to fall to half its initial level.

45
Q

What half-life be used to find?

A

The rate at which a source decays (its activity).

46
Q

Each time a radioactive nucleus decays to become a stable nucleus, what decreases?

A

The total activity.

47
Q

What does a short half-life mean for activity and why?

A

The activity decreases quickly because the nuclei arevert unstable and rapidly decay.

48
Q

What does a long half-life mean for activity and why?

A

The activity decreases slowly because most of the nuclei don’t decay for a long time.

49
Q

Why can sources with a short half-life be dangerous?

A

They emit a high amount of radiation at the start.

50
Q

Why can sources with a long half-life be dangerous?

A

Nearby areas are exposed to radiation for years.

51
Q

(got up to

A

radioactive contamination)

physics (30 decks)

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