Radiation

Question 1

Plum Pudding Model

Answer 1

The scientific idea that an atom is a sphere of positive charge, with negatively charged electrons in it.

Question 2

Rutherford and the Nucleus

Answer 2

• His two students, Hans Geiger and Ernest Marsden, directed a beam of alpha particles at a very thin gold leaf suspended in a vacuum.
• A very small number of alpha particles came straight back off the foil

Question 3

What did Bohr do ?

Answer 3

Neil’s Bohr suggested that the electrons orbited the nucleus in different energy levels or at specific distances from the nucleus.

Question 4

What did James Chadwick discover ?

Answer 4

neutron

Question 5

Nucleus

Answer 5

The central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. The plural of nucleus is nuclei.

Question 6

Atom Size

Answer 6

Atoms are very small, they have a radius of around 1 × 10-10 metres.

Question 7

Mass Number

Answer 7

The total number of protons and neutrons is called the mass number

Question 8

Atomic Number

Answer 8

The number of protons is called the atomic number

Question 9

What is an Isotope ?

Answer 9

Isotopes are forms of an element that have the same number of protons but different numbers of neutrons.

Question 10

What is an Ion ?

Answer 10

Electrically charged particle, formed when an atom or molecule gains or loses electrons.

Question 11

How can a nucleus be stable ?

Answer 11

An atom’s nucleus can only be stable if it has a certain amount of neutrons for the amount of protons it has.

Question 12

What is an Alpha particle

Answer 12

Alpha decay causes the mass number of the nucleus to decrease by four and the atomic number of the nucleus to decrease by two.

Question 13

How does Beta Decay Work ?

Answer 13

If the nucleus has too many neutrons, a neutron will turn into a proton and emit a fast-moving electron. This electron is called a beta (β) particle - this process is known as beta radiation.

Question 14

What is a Beta Particle

Answer 14

A beta particle has a relative mass of zero, so its mass number is zero, and as the beta particle is an electron.

Question 15

How does a nucleus lose energy ?

Answer 15

After emitting an alpha or beta particle, the nucleus will often still be too ‘hot’ and will lose energy in a similar way to how a hot gas cools down.

Question 16

Gamma Ray Emission

Answer 16

Gamma ray emission causes no change in the number of particles in the nucleus meaning both the atomic number and mass number remain the same.

Question 17

Neutron Emmision

Answer 17

Occasionally it is possible for a neutron to be emitted by radioactive decay.

Neutron emission causes the mass number of the nucleus to decrease by one and the atomic number remains the same.

Question 18

Alpha Penetration Levels

Answer 18

α Skin/paper High < 5 centimetre (cm)

Question 19

Beta Penetration Levels

Answer 19

β 3 mm aluminium foil Low ≈ 1 metre (m)

Question 20

Gamma Penetration Levels

Answer 20

γ Lead/concrete Very low > 1 kilometre (km)

Question 21

What is the Half-life ?

Answer 21

Half-life is the time it takes for half of the unstable nuclei in a sample to decay or for the activity of the sample to halve or for the count rate to halve

Question 22

Count Rate

Answer 22

Count-rate is the number of decays recorded each second by a detector, such as the Geiger-Muller tube.

Question 23

Penetration Power

Answer 23

The power of the radiation that demonstrates how far into a material the radiation will go.

Question 24

Radiation

Answer 24

When unstable atoms give off particles that can be harmful to humans.

Question 25

Radioactive Decay

Answer 25

The process in which unstable atomic nuclei emit ionising radiation to become stable.

Question 26

Sterilisation Advantages

Answer 26

sterilisation can be done without high temperatures

it can be used to kill bacteria on things that would melt

Question 27

Sterilisation Disadvantages

Answer 27

it may not kill all bacteria on an object

it can be very harmful - standing in the environment
where objects are being treated by irradiation could expose people’s cells to damage and mutation

Question 28

Eyes

Answer 28

High doses can cause cataracts.

Question 29

Thyroid

Answer 29

Radioactive iodine can build up and cause cancer, particularly during growth.

Question 30

Lungs

Answer 30

Breathing in radioisotopes can damage DNA.

Question 31

Stomach

Answer 31

Radioactive isotopes can sit in the stomach and irradiate for a long time.

Question 32

Reproductive organs

Answer 32

High doses can cause sterility or mutations.

Question 33

Skin Radiation

Answer 33

Can burn skin or cause cancer.

Question 34

Bone marrow

Answer 34

Radiation can cause leukaemia and other diseases of the blood.

Question 35

How to Stay Radioactive Safe

Answer 35

keep radioactive sources like technetium-99 shielded in a lead-lined box when not in use

wear protective clothing

avoid contact with bare skin and do not attempt to taste the sources

wear face masks to avoid breathing in materials

limit exposure time

handle radioactive materials with tongs

a safer distance

Question 36

Decays per second

Answer 36

The number of decays of a radioactive element per second. Measured in Becquerels (Bq).

Question 37

Background Radiation

Answer 37

Low level nuclear radiation that is always present from natural and man-made sources

Question 38

Irraditation

Answer 38

A substance is contaminated if another substance is mixed or dispersed within it.

Question 39

A radioisotope

Answer 39

A radioisotope used to trace, eg the flow of blood through an organ.

Question 40

Sterilisation

Answer 40

The process of ensuring that a sample contains no living things

Question 41

Nuclear Fusion

Answer 41

The joining together of two smaller atomic nuclei to produce a larger nucleus.

Question 42

Nuclear Fission

Answer 42

The splitting of a large nucleus to produce two smaller ones. Two or three neutrons are also released in the process. The energy from the neutrons powers a nuclear reactor.