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Physics Y10&Y11 > Atomic and Nuclear Physics > Flashcards

Atomic and Nuclear Physics Flashcards

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1
Q

Describe the model of the atom:

A

There is a tiny, dense, positively charged nucleus at the centre of ‘empty space’ with an electron cloud

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2
Q

To what order is the diameter of the atom?

A

~10^-10

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3
Q

To what order is the diameter of the nucleus?

A

~10^-15

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4
Q

What is the charge of a proton?

A

+1.6 x 10^-19 C

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5
Q

What is the charge of a neutron?

A

0C

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6
Q

What is the charge of a electron?

A

-1.6 x 10^-19 C

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7
Q

How would an isotope be defined?

A

A form of an element that has the same number of protons but a different number of neutrons compared to the most abundant form.

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8
Q

What is the nucleon number?

A

The number of protons and neutrons in the nucleus of an atom

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9
Q

A radioactive substance contains unstable nuclei. What do unstable nuclei have?

A

An inbalance of energy between the nucleons

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10
Q

How does a particle become more stable?

A

By improving the balance of energy between the nucleons.

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11
Q

How is the balance of energy between the nucleons improved?

A

By emitting energy from the nucleus in the form of: -Mass -Electromagnetic radiation (carried by photons)

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12
Q

Alpha Decay is a mechanism of radioactive decay, what does it do?

A

Ejects two protons and two neutrons (as a single particle) from the nucleus

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13
Q

What is Beta decay?

A

The emission of an electron from the nucleus- a neutron turns into a proton and emits an electron

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14
Q

What is gamma decay?

A

The emission of high frequency (high energy) electromagnetic radiation from the nucleus

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15
Q

What does ionising ability indicate?

A

How much each radiation type interacts with matter

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16
Q

What is the relative charge of an alpha particle?

A

+2 (two protons)

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17
Q

What is the relative charge of a beta particle?

A

-1 (one electron)

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18
Q

What is the relative charge of a gamma particle?

A

0

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19
Q

What is the relative mass if an alpha particle?

A

7000

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20
Q

What is the relative mass of a beta particle?

A

1

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21
Q

What is the relative mass of a gamma particle?

A

0

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22
Q

What is the range in air for alpha radiation?

A

a few centimetres

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23
Q

What is the range in air for beta radiation?

A

of the order of a metre

24
Q

What is the range in air for gamma radiation?

A

infinite

25
Q

What is alpha radiation stopped by?

A

-Paper -Skin

26
Q

What is beta radiation stopped by?

A

a few millimetres of aluminium

27
Q

What is gamma radiation stopped by?

A

Many centimetres of lead or metres of concrete (sometimes combination)

28
Q

What is the ionising ability of alpha radiation?

A

Very high

29
Q

What is the ionising ability of beta radiation?

A

Low (medium)

30
Q

What is the ionising ability of gamma radiation?

A

Very low

31
Q

What type of process is radioactive decay?

A

random

32
Q

What does a Geiger counter detect?

A

Emitted waves or particles from a sample

33
Q

What does a Geiger counter display to show the radiation?

A

A count rate

34
Q

What did Rutherford observe happen to alpha particles in his gold leaf experiment in 1911?

A

That some alpha particles went through the thin metal foil but others were scattered by large angles

35
Q

What was Rutherfords new model?

A

Most the atom is empty space but there is a small, massive, positively charged nucleus in the centre of the atom with electrons orbiting around it

36
Q

How did Rutherford’s model fit in with his observations made in the experiment?

A

Most of the alpha particles went through the foil, so most the atom is empty space. Some alpha particles were scattered back, so there is a very small, dense, positively charged nucleus at the centre of the atom which repels the positive alpha particles

37
Q

Compare the changes in the nucleus with alpha and beta decay

A

In alpha decay, the nucleus loses 4 particles, 2 protons and 2 neutrons so the nucleon number decreases by 4. In beta decay, the nucleon number remains the same as the nucleus loses 1 neutron but gains 1 proton

38
Q

Compare gamma emission and neutron emission

A

In both, an uncharged particle/wave are emitted and the element remains the same. In gamma however, an electromagnetic wave is emitted and the mass of the atom stays the same. In neutron emission, a particle is emitted so the mass decreases.

39
Q

Define irradiation

A

A process by which a substance is exposed to radiation (and is therefore not the actual source of radiation)

40
Q

How can we tell if alpha radiation is being emitted by a sample?

A

Set up a Geiger counter so it is detecting radiation from the sample.. Put a sheet of paper between the counter and sample. If the count rate of the counter goes down, the sample is emitting alpha radiation

41
Q

How can we tell if beta radiation is being emitted by a sample?

A

Set up the same process as for alpha radiation but if the count rate doesn’t go down for a sheet of paper, but does go down for a sheet of aluminium, the sample is emitting beta radiation.

42
Q

How can we tell if gamma radiation is being emitted by a sample?

A

If the count rate on the Geiger counter remains the same if paper and aluminum have been put between the counter and sample, the sample is emitting gamma radiation.

43
Q

Timeline of model of atom discovery:

A

1897 - J.J. Thompson discovers electrons 1911 - Ernest rutherford creates nuclear model 1913 - Bohr discovers the energy levels for electrons 1924 - de Broglie establishes wave nature of electrons 1932 - Chadwick discovers the existence of the neutron

44
Q

What does gamma radiation have a high something of?

A

Penetration ability

45
Q

What are two hazards associated with handling radioactive materials?

A

Irradiation Contamination

46
Q

What is radioactive contamination?

A

Particles of radioactive material left on an object

47
Q

What kind of process is radioactive decay? Why?

A

Random process as it is impossible to predict which specific nuclei will undergo decay at any particular instant

48
Q

How can patterns still emerge from the randomness of radioactive decay?

A

Because of the enormous numbers of radioactive nuclei presentin even a small sample

49
Q

What is activity?

A

The number of decays per second

50
Q

What is the activity of a sample dependent on?

A

The number of radioactive nuclei in the sample

51
Q

What is activity measured in?

A

Becquerel, Bq

52
Q

What does 1Bq represent?

A

One decay per second

53
Q

What is the relationship between the activity and number of radioactive nuclei in a sample?

A

Directly proportional

54
Q

Define the half-life of a substance:

A

the time taken for the number of radioactive nuclei in a sample to reduce by half

55
Q

Is half-life independent or dependent of the size of the sample?

A

Independent

56
Q

What is the variation between the half lives of substances?

A

From billions of years to billionths of a second

57
Q

What type of decay (related to maths) is the decay of radioactive substances?

A

A true exponential

Physics Y10&Y11 (17 decks)

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