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1

State the typical size of an atom

1 x 10 -10 m

2

Describe the structure of an atom

A positively charge nucleus containing protons and neutrons surrounded by negatively charged electrons

3

State the size of a nucleus compared to an atom

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

4

How can electrons move to a higher energy shell/level

By absorbing electromagnetic radiation

5

How can electrons move to a lower energy shell/level

By releasing electromagnetic radiation

6

What is the charge on an atom why?

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

7

What is an Ion?

A charged atom that has gained or lost electrons

8

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

Protons

9

Define the atomic number

Number of protons = number of electrons for an atom

10

Define nucleon number

mass mummer = Number of protons + number of neutrons

11

Define an isotope

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

12

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

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.
Niels Bohr suggested that electrons orbited the nucleus in shells
James Chadwich discovered the neutron

13

Describe the plum pudding model of the atom

A positive sphere with negative electrons dotted throughout it.

14

Describe the alpha particle scattering experiment.

Alpha Particles were fired at thin gold in a vacuum.

15

Describe and explain the observations from the alpha particle experiment.

The majority of alpha particles went straight though the gold. so atoms are mainly empty space.
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)
A tiny fraction of alpha particles bounced back where they came from. the nucleus must be a tiny part of the atom

16

How can an unstable nucleus become more stable?

By giving out radiation (alpha, beta or gamma)

17

Define activity

The rate at which a source of unstable nuclei decays

18

State the units of activity

Becquerel (Bq)

19

Define count rate

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

20

Describe a alpha particle

Two protons and two neutrons together. A helium nucleus

21

Describe a beta partice

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

22

Describe a gamma ray

An electromagnetic wave with no charge or mass.

23

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

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

24

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

Ionising ability is the ability to do damage to our living cells and tissues.
Alpha - highly ionising
Beta - moderately ionising
Gamma - very weakly ionising

25

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

mass number = 4
proton number = 2

26

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

mass number = 0
proton number = -1

27

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

mass number = 0
proton number = 0

28

how can the rate of radioactive decay be increased?

It can be affected by physics quantities such as temperature or pressure. it is completely random.

29

Define half life

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

30

Define contamination

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

31

Define irradiation

The process of exposing an object to radiation. the object does become radioactive. e.g. killing bacterial on fruit to increase its shelf life.

32

How should radioactive sources be used safely?

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

33

What is background radiation?

Radiation that is around us all the time

34

State some sources of natural background radiation?

Rocks, cosmic rays, food

35

State some sources of man made background radiation

X-rays, nuclear bombs, nuclear power stations

36

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

occupation e.g. radiotherapist, pilot
Location - Background radiation increase with altitude.

37

State the units of radiation dose

Sieverts (Sv)

38

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

Gamma with a short half life - 6 hours

39

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

Alpha with a long half life - 400 years

40

Describe nuclear fission

Splitting of a large unstable nucleus eg Uranium or plutonium

41

What is required to start fission

The unstable nucleus must absorb a neutron

42

What is released after fission

2/3 neutrons
Lots of energy

43

What is a chain reaction?

One neutron is absorbs by one Uranium nucleus. this undergoes fission and realises 2 or 3 neutrons. these neutrons can cause fission in 2 or 3 more uranium nucleus. the process can keep repeating.

44

Describe nuclear fusion

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

45

Where does fusion take place naturally?

In all stars

46

What is released by fusion

Energy

47

What is the majority of the mass of an atom?

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

48

What was Dalton's theory about the atom?

all matter is made of small invisible units called atoms

49

What was Thomson's theory about the atom?

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

50

What was Rutherford's theory about the atom?

following the alpha particle scattering experiment he update 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

51

What was Bohr's theory about the atom?

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

52

What was Chadwick's theory about the atom?

discovered the neutron

53

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

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

54

What are the different types of nuclear radiation?

Alpha
Beta
Gamma
Neutron

55

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

Mass (nucleon) number goes down by 4
Number of protons goes does by 2

56

What happens during beta decay?

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

57

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

Mass (nucleon) number stays the same
Number of protons goes up by 1

58

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

Mass (nucleon) number stays the same
Number of protons stays the same

59

What happens when radioactive radiation strikes an atom?

It can knock an electron off an atom - ionisation

60

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

Gamma as it's the least ionising and escapes easily

61

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

Alpha as it's most ionising and cannot escape

62

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

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