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Lamda > Radioactivity > Flashcards

Radioactivity Flashcards

1
Q

The nuclei of radioactive substances are ………..

A

Unstable

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2
Q

How do radioactive substances become stable

A

Radioactive decay

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3
Q

What do radioactive substances do during radioactive decay?

A

They emit radiation and turn into other elements

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4
Q

Can we predict when an unstable nuclei will decay?

A

No, it is a random process and is not affected by external conditions

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5
Q

What is background radiation?

A

Radiation from radioactive substances in the environment, from space, from devises such as x-Ray’s which is around us all the time

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6
Q

Why did the model of the atom become know as the plum pudding model?

A

At the time scientists thought that atoms consisted of spheres of positive charge which electrons stuck into them, like plums in a pudding

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7
Q

What did the alpha scattering experiment consist of?

A

Rutherford, Geiger and mars den fired alpha particles at thin gold foil

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8
Q

Most of the alpha particles passed straight through the foil what does this mean about the atom?

A

Most of the atom is just empty space

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9
Q

Some of the alpha particles were deflected through small angles what does this tell us about the nucleus?

A

It has a positive charge

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10
Q

A frpew alpha particles rebound through very large angles what does this suggest about the nucleus?

A

It has a large mass and a very large positive charge

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11
Q

What did the alpha particle scattering experiment suggest about the structure of the nucleus?

A

It is where most of the mass of the atom is concentrated, very small and positive,y charged

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12
Q

What change occurs in the nucleus in alpha decay?

A

The nucleus loses 2 protons and 2 neutrons

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13
Q

What particles are emitted in alpha decay

A

2 protons & 2 neutrons as an α particle

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14
Q

What change in the nucleus occurs in beta decay?

A

A neutron in the nucleus changes into a proton and an electron

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15
Q

What particles is emitted in beta decay?

A

The electron created in the nucleus is instantly emitted

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16
Q

Give the relative mass of a proton, neutron and electron

A

P - 1
N - 1
E - 0.0005

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17
Q

What are the relative charges of protons neutrons and electrons

A

P - +1
N- 0
E -1

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18
Q

Why does an atom have no overall charge?

A

They have the same no of protons and electrons

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19
Q

When does an atom become an ion?

A

When it loses or gains electrons and becomes charged

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20
Q

All atoms of a particular element have the same number of ………..

A

Protons

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21
Q

What is an isotope?

A

An atom of the same element with different numbers of neutrons

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22
Q

What is the atomic number?

A

The number of protons in an atom

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23
Q

What is the mass number?

A

The total number of protons plus neutrons

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24
Q

What does an alpha particle consist of?

A

2protons

2 neutrons

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25
Q

What is the relative mass of an alpha particle?

A

4

26
Q

What is the relative charge of an alpha particle?

A

+2

27
Q

When a nucleus emits an alpha particle the ………. number goes down by …… And the ……… Number goes down by …….

A

Atomic
2
Mass
4

28
Q

What does the nucleus contain?

A

Protons, neutrons and electrons

29
Q

What is a beta particle?

A

A high speed electron from the nucleus emitted when a neutron in the nucleus changes to a proton and an electron

30
Q

What is the relative mass of a beta particle?

A

0

31
Q

What is the relative charge of a beta particle?

A

-1

32
Q

In beta decay the …….. Stays in the nucleus so the …….. Number goes up by …… And the …….. Number is …………… The …….. Is instantly emitted

A 
Proton 
Atomic 
1 
Mass number 
unchanged 
Electron
33
Q

What happens when a nucleus emits gamma radiation?

A

There is no change in the atomic or mass number

34
Q

A ……… Ray is an …………… Wave released from the ………… It has no …….. And no ………. Mass

A 
Gamma 
Electromagnetic 
Nucleus
Charge 
Mass
35
Q

What will happen when nuclear radiation passes through a material?

A

It will collide with the atoms, knocking of electrons and creating ions (ionisation)

36
Q

What can ionisation do to a living cell?

A

Damage or kill the cell

37
Q

What are alpha particles strongly ionising

A

They are relatively large so have lots of collisions with atoms

38
Q

Why will an alpha particle not penetrate a material very far?

A

As it is strongly ionising

39
Q

What can alpha particles be stopped by

A

Thin paper, human skin or few cm of air

40
Q

are alpha particles deflected by electric and magnetic firlds?

A

They have a positive charge so are deflected

41
Q

What are beta particles like compared to alpha?

A

Beta particles are much smaller and faster than alphas so they are less ionising but penetrate further

42
Q

What are beta particles stopped by?

A

Few m of air, thin sheet of aluminium

43
Q

Are beta particles affected by a magnetic or electric field?

A

They have a negative charge so are deflected in the opposite direction to alpha

44
Q

Gamma rays are electromagnetic waves so will travel a ……. Way before ……. With ……..

A

Long
Colliding
Atoms

45
Q

Gamma days are….

A

Weakly ionising and very penetrating

46
Q

What will absorb gamma radiation?

A

Several metres of concrete

Or cm of lead

47
Q

Are gamma rays deflected by electric or magnetic fields

A

No

48
Q

What happens to the count rate of a radioactive sample over time?

A

Decreases

49
Q

What is the half life?

A

The time is takes for the number of unstable nuclei in a sample to halve
Or
The time taken for the count rate from the original isotope to fall to half its initial value

50
Q

Th half life is the ……. for any sample of a particular ………

A

Same

Isotope

51
Q

What would happen to the original count rate of a radioactive sample after two half lives have passed?

A

It will have decreased to one quatre of the original value

52
Q

What are alpha sources used for?

A

In smoke alarms

53
Q

What half life will an alpha source need for a smoke alarm?

A

A few years

54
Q

What are beta sources used for?

A

Thickness monitoring

55
Q

Why is beta radiation used for thickness monitoring?

A

Alpha particles would be stopped by the thin paper and gamma rays would pass through and be unable to detect small changes in thickness

56
Q

What sort of half life will a beta source for thickness monitoring need?

A

Many years so that decreases in count rate are due to changes in the thickness of the paper

57
Q

What are gamma and beta sources used as?

A

Tracers in medicine

58
Q

What half life will of a gamma or beta tracer need to be?

A

A half life of a few hours ago that the patient is not exposed to unnecessary radiation

59
Q

What is radioactive dating used for

A

Used to find the age of ancient material

60
Q

What is carbon dating used for.

A

To find the age of wood and other organic material

61
Q

What is used to find the age of igneous rocks

A

Uranium

Lamda (4 decks)

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