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11BT > Atomic Physics - Paper 1 > Flashcards

Atomic Physics - Paper 1 Flashcards

To revise Atomic physics (paper 1)

1
Q

State the typical size of an atom

A

1 x 10-10 m

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2
Q

Describe the structure of an atom

A

A positively charged nucleus containing protons and neutrons surrounded by negatively charged electrons in shells.

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3
Q

State the size of a typical nucleus?

A

1 x 10-15 m

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4
Q

State the size of a nucleus compared to an atom

A

The radius of the nucleus is less than 1/10000 of the radius of an atom

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5
Q

How can electrons move to a higher energy shell/level

A

By absorbing energy in the form of electromagnetic radiation. This is called excitation.

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6
Q

How can electrons move to a lower energy shell/level

A

By releasing energy in the form of electromagnetic radiation. This is called relaxation.

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7
Q

What is the charge on an atom why?

A

Atoms are neutral as the number of positive protons is equal to the number of negative electrons

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8
Q

What is an Ion?

A

A charged atom that has gained or lost electrons

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9
Q

The same element must always have the same number of…?

A

Protons

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10
Q

Define the atomic number

A

Number of protons = number of electrons for an atom

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11
Q

Define nucleon number

A

mass number = Number of protons + number of neutrons

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12
Q

Define an isotope

A

The same element with the same number of protons but with a different number of neutrons.

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13
Q

Describe how the model of the atom has changed with new experimental evidence

A

Atoms were originally though to be tiny spheres that couldn’t be divided.

The discovery of the electron led to the plum pudding model of the atom.

The alpha particle scattering experiment led to the nuclear model of the atom - a positive nucleus which contained the majority of the mass.

Neils Bohr suggested that electrons orbited the nucleus in shells.

James Chadwich discovered the neutron

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14
Q

Describe the plum pudding model of the atom

A

A positive sphere with negative electrons dotted throughout it.

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15
Q

Describe the alpha particle scattering experiment.

A

Alpha Particles were fired at thin gold in a vacuum.

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16
Q

Describe and explain the observations from the alpha particle experiment.

A
  1. The majority of alpha particles went straight though the gold. So atoms are mainly empty space.
  2. Some alpha particles were defected by the gold foil. There must be something positive which contained the majority of the mass in an atom (the nucleus)
  3. A tiny fraction of alpha particles bounced back where they came from. The nucleus must be a tiny part of the atom
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17
Q

How can an unstable nucleus become more stable?

A

By giving out radiation (alpha, beta or gamma)

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18
Q

Define activity

A

The rate at which a source of unstable nuclei decays

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19
Q

State the units of activity

A

Becquerel (Bq)

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20
Q

Define count rate

A

The number of decays recorded by a detector (GM tube)

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21
Q

Describe a alpha particle

A

Two protons and two neutrons together. A helium nucleus

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22
Q

Describe a beta partice

A

A fast moving electron ejected from the nucleus. This happens after a neutron has decayed into a proton

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23
Q

Describe a gamma ray

A

An electromagnetic wave with no charge or mass.

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24
Q

Define penertrating abilty

A

Penetrating power is what can stop the radiation.

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25
Q

State the penetrating power of alpha, beta and gamma radiation.

A

Penetrating power is what can stop the radiation.

Alpha - skin, paper 5 - 10 cm of air

Beta - mm’s of aluminium, 1 meter of air

Gamma - reduced by cm’s of lead or m’s of concrete

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26
Q

Define Ionisation ability

A

Ionising ability is the ability to do damage to our living cells and tissues.

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27
Q

State the ionising ability of alpha, beta and gamma radiation.

A

Ionising ability is the ability to do damage to our living cells and tissues. Alpha - highly ionising

Beta - moderately ionising

Gamma - very weakly ionising

28
Q

In decay equations what is the mass number and proton number for an alpha particle?

A

mass number = 4

proton number = 2

29
Q

In decay equations what is the mass number and proton number for a beta particle?

A

mass number = 0

proton number = -1

30
Q

In decay equations what is the mass number and proton number for a gamma wave?

A

mass number = 0

proton number = 0

31
Q

how can the rate of radioactive decay be increased?

A

It can’t be affected by physics quantities such as temperature or pressure. it is completely random.

32
Q

Define half life

A

The time taken for the number of radioactive nuclei in a sample to half.

33
Q

Define contamination

A

Unwanted presence of radioactive atoms on other materials such as clothes, buildings etc

34
Q

Define irradiation

A

The process of exposing an object to radiation. The object does not become radioactive. e.g. killing bacterial on fruit to increase its shelf life.

35
Q

How should radioactive sources be used safely?

A

Use only for a short period of time.

Keep source at arms length.

Point source away from yourself.

Stored in a lead lined box with a radioactive symbol

36
Q

What is background radiation?

A

Radiation that is around us all the time

37
Q

State some sources of natural background radiation?

A

Rocks, cosmic rays, food

38
Q

State some sources of man made background radiation

A

X-rays, nuclear bombs, nuclear power stations

39
Q

What factors can affect the level of background radiation a person receives?

A

occupation e.g. radiotherapist, pilot

Location - Background radiation increase with altitude.

40
Q

State the units of radiation dose

A

Sieverts (Sv)

41
Q

What type of radiation and half life should be used with a medical tracer.

A

Gamma with a short half life - 6 hours.

Gamma is the least ionising so wil cause the least amount of damage to the patient.

42
Q

What type of radiation and half life should be used with a smoke detector.

A

Alpha with a long half life - 400 years

Alpha particles are highly ionising so they can be easily stopped by smoke and set the alarm off.

43
Q

Describe nuclear fission

A

Splitting of a large unstable nucleus eg Uranium or plutonium

44
Q

What is required to start fission

A

The unstable nucleus must absorb a neutron

45
Q

What is released after fission

A

2 or 3 neutrons and lots of energy

46
Q

What is a chain reaction?

A

One neutron is absorbs by one Uranium nucleus. This undergoes fission and releases 2 or 3 neutrons. These neutrons can cause fission in 2 or 3 more uranium nuclei. the process can keep repeating.

47
Q

Describe nuclear fusion

A

The joining of two light nuclei to form a heavier nucleus.

48
Q

Where does fusion take place naturally?

A

In all stars

49
Q

What is released by fusion

A

Energy

50
Q

Where is the majority of the mass of an atom?

A

The nucleus, as the mass of an electron is almost zero compared to the mass of protons and neutrons

51
Q

What was Dalton’s theory about the atom?

A

all matter is made of small invisible units called atoms

52
Q

What was Thomson’s theory about the atom?

A

He discovered the electron and therefore knew the atom was made up of charged particles. He introduced the Plum Pudding Model

53
Q

What was Rutherford’s theory about the atom?

A

following the alpha particle scattering experiment he updated the plum pudding model to the Nuclear Model; that most of the mass of the atom was concentrated in the nucleus which carries a positive charge

54
Q

What was Bohr’s theory about the atom?

A

Bohr updated the Nuclear model to show that electrons orbit the nucleus in certain energy levels

55
Q

What was Chadwick’s theory about the atom?

A

He discovered the neutron

56
Q

Why did the discovery of electrons mean that Dalton’s model of the atom needed to be updated?

A

That atoms were not the smallest thing anymore, as the electron was smaller than the atom

57
Q

What are the different types of nuclear radiation?

A

Alpha, Beta, Gamma and Neutron

58
Q

What happens to the mass and charge of the nucleus during alpha decay?

A

Mass (nucleon) number goes down by 4

Number of protons goes does by 2

59
Q

What happens during beta decay?

A

A neutron decays into a proton creating the beta particle which is fired out of the nucleus

60
Q

What happens to the mass and charge of the nucleus during beta decay?

A

Mass (nucleon) number stays the same

Number of protons goes up by 1

61
Q

What happens to the mass and charge of the nucleus during gamma decay?

A

Mass (nucleon) number stays the same

Number of protons stays the same

62
Q

What happens when radioactive radiation strikes an atom?

A

It can knock an electron off an atom - ionisation

63
Q

What is the safest type of radiation to have inside the body?

A

Gamma as it’s the least ionising and escapes easily

64
Q

What is the most dangerous type of radiation to have inside the body?

A

Alpha as it’s most ionising and cannot escape

65
Q

What is the safest type of radiation to have outside the body?

A

Alpha as it’s least penetrating and can’t penetrate our skin

11BT (18 decks)

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