8. Radioactivity Flashcards Preview

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Flashcards in 8. Radioactivity Deck (77)
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1
Q

Relative mass of a proton

A

1

2
Q

Relative mass is the mass compared with that of a …

A

Proton

3
Q

Relative charge of a proton

A

+1

4
Q

Location of a proton

A

Within the nucleus

5
Q

Relative mass of a neutron

A

1

6
Q

Relative charge of a neutron

A

0

7
Q

Location of a neutron

A

Within the nucleus

8
Q

Relative mass of an electron

A

1/1840

9
Q

Relative charge of an electron

A

-1

10
Q

Location of an electron

A

In circular shells orbiting the nucleus

11
Q

All nuclei, except the … nucleus, contain both protons and neutrons

A

hydrogen

12
Q

Name the three types of radiation and their symbols

A

Alpha (a), beta (ß) and gamma (γ)

13
Q

Radiation is emitted from the nuclei of heavy atoms. What is a heavy atom?

A

A heavy atom has a nucleus containing a large number of protons and neutrons and its nucleus is unstable.

14
Q

What happens to an unstable nucleus?

A

It decays and emits radiation.

15
Q

All types of radiation originate from an …

A

Unstable nucleus

16
Q

Nature of alpha radiation

A

Particle

17
Q

Nature of beta radiation

A

Particle

18
Q

Nature of gamma radiation

A

Wave

19
Q

Relative charge of alpha radiation

A

+2

20
Q

Relative charge of beta radiation

A

-1

21
Q

Relative charge of gamma radiation

A

Uncharged

22
Q

Relative mass of alpha radiation

A

4

23
Q

Relative mass of beta radiation

A

1/1840

24
Q

Relative mass of gamma radiation

A

Zero

25
Q

Identity of alpha radiation

A

Helium nucleus consisting of two protons and two neutrons

26
Q

Identity of beta radiation

A

Fast moving electron

27
Q

Identity of gamma radiation

A

Electromagnetic wave of high energy

28
Q

Ionising power of alpha radiation

A

Enormous

29
Q

Ionising power of beta radiation

A

Moderate

30
Q

Ionising power of gamma radiation

A

Poor

31
Q

Penetrating ability of alpha radiation

A

Stopped by 2-4 cm of air or thin tissue paper

32
Q

Penetrating ability of beta radiation

A

Stopped by several metres of air or about 5 mm of aluminium

33
Q

Penetrating ability of gamma radiation

A

Thick lead is an effective shield but cannot stop the radiation completely

34
Q

Describe the plum pudding model of the atom

A

The atom consisted of negatively charged electrons embedded in a uniform, positively charged sphere like currants in a bun, in sufficient numbers to make the atom as a whole electrically neutral.

35
Q

How did Rutherford detect the alpha particles during his alpha particle scattering experiment?

A

The alpha particles were detected by flashes of light that they produced when they hit a glass screen coated with zinc sulphide.

36
Q

Why was the alpha particle scattering experiment carried out in a vacuum?

A

To prevent collisions between alpha particles and air atoms

37
Q

What does the alpha particle scattering experiment serve as evidence for?

A

The existence of nuclei

38
Q

What did Rutherford’s alpha particle scattering experiment involve?

A

Rutherford fired positively charged alpha particles from an alpha source at a positively charged thin gold foil inside a vacuum.
He set up a glass screen coated with zinc sulphide and a microscope to detect when alpha particles hit it, producing a flash of light.

39
Q

Describe the observations of the alpha particle scattering experiment

A
  1. Most alpha particles were undeflected by the gold foil
  2. Some alpha particles were scattered through large angles
  3. About 1 in 8000 alpha particles were back-scattered through very large angles.
40
Q

Because most of the alpha particles missed the nucleus, it had to be …

A

Very small

41
Q

Since the nucleus appeared to repel the positively charged alpha particles, it had to be …

A

Positively charged, since like charges repel

42
Q

Why did most of the alpha particles pass straight through the atom during the alpha particle scattering experiment?

A

Rutherford correctly argued that most of the atom is just empty space.

43
Q

What did Rutherford realise because of the fact that the electron was so light?

A

Most of the atom’s mass was contained within the nucleus itself.

44
Q

How did Rutherford explain why certain elements would give out light?

A

Rutherford suggested that the electrons orbited the nucleus in circular paths.

45
Q

What did Rutherford find the negative charge to be?

A

A cloud of electrons surrounding the positive nucleus

46
Q

Rutherford’s alpha particle scattering experiment lead to the abandonment of the …

A

Plum pudding model

47
Q

The model of the atom accepted by physicists today is the …

A

Rutherford-Bohr model

48
Q

Define a nucleon

A

A proton or neutron

49
Q

The value of A is …

A

The relative mass of the nucleus compared to the proton

50
Q

Z gives the number of …

A

Protons within the nucleus and hence the charge of the nucleus.

51
Q

Notation:
A =
Z =
X =

A
A = mass number
Z = atomic number
X = chemical symbol of the element     
For A
          X
       Z
52
Q

Symbol for a beta particle

A

0
e
-1

53
Q

Symbol for a proton

A

1
p
1

54
Q

Symbol for a neutron

A

1
n
0

55
Q

Symbol for an alpha particle

A
4
  a
2 
Or
4
  He
2
56
Q

Define isotopes

A

Isotopes are atoms of an element with the same atomic number but different mass numbers indicating a different number of neutrons

57
Q

Isotopes are caused by different numbers of … but same numbers of protons, the latter meaning it is the same element

A

neutrons

58
Q

What is the number in Uranium-235?

A

The mass number

59
Q

In a nuclear disintegration equation, the mass numbers and the atomic numbers on both sides must …

A

Balance

60
Q

An * in a nuclear disintegration equation indicates that an element …

A

Is in an excited state

61
Q

The new element formed in a nuclear disintegration equation is called the …

A

Daughter nucleus

62
Q

When writing a gamma ray symbol in a nuclear disintegration equation, you write it without …

A

Numbers, as they have neither mass nor charge

63
Q

Name a nuclear radiation detector and state briefly how it works

A

Geiger-Müller (GM) tube connected to a counter, which detects and measures radiation in counts per minute

64
Q

Define background radiation

A

Background radiation is radiation from natural sources all around us, for example from the human body

65
Q

Actual count rate =

A

Measured count rate - background activity

66
Q

Define an ion

A

An electrically charged particle obtained from an atom by adding or removed electrons

67
Q

Define ionisation

A

The process of changing a neutral atom into an ion

68
Q

How does ionisation happen?

A

Ionising radiation passes through an atom and knocks an electron out of orbit around the positive nucleus, forming a positive ion.

69
Q

Alpha particles, beta particles and gamma rays are called …

A

Ionising radiations - because they can remove orbiting oelectrons from atoms as they collide with them, leaving behind a positive ion

70
Q

Explain how ionising ability is related to penetrating ability.

A

Highly ionising radiation loses energy rapidly and will therefore have less penetrating ability.
Weakly ionising radiation interacts little with matter and will therefore be very penetrating.

71
Q

Explain why alpha, beta and gamma are dangerous ionising radiations.

A

They can disrupt the DNA contained within cells and cause cancer.

72
Q

State safety precautions for using radioactive materials

A
  1. Radioactive sources should be stored in a lead-lined box in a locked cabinet
  2. Experiments with radioactive sources should be done as quickly as possible to minimise exposure to radiation
  3. Individual sources should be handled with forceps at arm’s length
  4. Students under 16 years old should never handle radioactive sources at all.
73
Q

Define half life

A

The time taken for the activity of a radioactive material to fall to half of its original value

74
Q

The activity of a radioactive material is measured in …

A

Becquerels (Bq), where 1 Bq means 1 disintegration per second

75
Q

Give two uses of radiation in industry

A

Controlling the thickness of steel in rolling mills and detecting leaks in underground pipes

76
Q

Why must a radioactive tracer used to detect leaks underground in pipes have a short half life?

A

To ensure that the source quickly disappears from the soil

77
Q

Give a use of gamma radiation

A

Sterilisation of surgical instruments