Topic 4 - Nuclear radiation

Question 1

Describe how the model of the atom has changed over time

Answer 1

• 1804 - John Dalton thought each element was made up of a different type of atom
• 1900ish - J.J.Thompson thought atoms were spheres of positive charge with negative electrons throughout (plum pudding)
• 1909 - Rutherford used alpha scattering experiment and found out that most of the mass of the atom must be in nucleus and rest was empty space
• Niels Bohr said electrons orbiting the nucleus do so at certain distances called energy levels
• 1932 - James Chadwick proved the existence of the neutron

Question 2

Define isotopes

Answer 2

Isotopes of an element are atoms with the same number of protons but a different number of neutrons (mass number is different)

Question 3

Describe alpha radiation

Answer 3

• when an alpha particle is emitted from the nucleus
• an alpha particle is 2 neutrons and 2 protons (like helium nuclei)

Question 4

Describe a beta particle

Answer 4

a fast-moving electron released by the nucleus

Question 5

Describe gamma rays

Answer 5

waves of electromagnetic radiation released by the nucleus

Question 6

Compare the penetrating power of alpha, beta and gamma radiation

Answer 6

• alpha is stopped by paper/skin (weak)
• beta is stopped by few mm of aluminium (medium)
• gamma is reduced by few cm of lead but never stopped (strong)

Question 7

Compare the ionising power of alpha, beta and gamma radiation

Answer 7

• alpha is strongly ionising (most)
• beta is weakly ionising (medium)
• gamma is very weakly ionising (least)

Question 8

Compare the range of radiation in the air of alpha, beta and gamma radiation

Answer 8

• alpha is a few cm (shortest)
• beta is a few metres
• gamma is around a km (longest)

Question 9

Compare the danger outside of the body of alpha, beta and gamma radiation

Answer 9

• alpha is the least dangerous
• beta is medium
• gamma is the most dangerous

Question 10

Compare the danger inside of the body of alpha, beta and gamma radiation

Answer 10

• alpha is the most dangerous
• beta is medium
• gamma is the least dangerous

Question 11

Compare how affected alpha, beta and gamma radiation are by an electric/magnetic field

Answer 11

• alpha is weakly deflected
• beta is strongly deflected
• gamma is not deflected

Question 12

Define ionisation

Answer 12

when a neutral atom loses or gains an electron (becomes charged)

Question 13

What happens in alpha decay?

Answer 13

an unstable nucleus emits an alpha particle

Question 14

What does an alpha decay equation look like?

Answer 14

unstable nucleus –> stable nucleus + alpha particle
(remember the mass and atomic numbers must be equal on both sides)

Question 15

What happens in beta decay?

Answer 15

a neutron in the nucleus turns into a proton and releases a fast-moving electron

Question 16

What does a beta decay equation look like?

Answer 16

unstable nucleus –> stable nucleus + beta particle (electron)
(remember the mass and atomic numbers must be equal on both sides)

Question 17

Define half-life

Answer 17

the time it takes for the number of radioactive nuclei in a sample to halve

Question 18

What is activity measured in?

Answer 18

Becquerels (Bq)

Question 19

How do you measure half-life using a graph?

Answer 19

• find half of the count rate
• draw a horizontal line across till it reaches the curve
• draw a vertical line down from the point it reaches the curve (this is 1 half life)

Question 20

Define background radiation

Answer 20

low-level radiation that’s around us all the time

Question 21

Define irradation

Answer 21

the process of exposing an object to a source of radiation

Question 22

Name 2 advantages of irradation

Answer 22

• can be used for sterilisation (removes need for high temps)
• can be used to kill bacteria

Question 23

Name 2 disadvantages of using irradation

Answer 23

• might not kill all bacteria on an object
• can be very harmful - causes cell damage and mutation

Question 24

What are ways of protecting yourself from irradation?

Answer 24

• lead-lined boxes
• standing behind barriers
• keeping at a safe distance

Question 25

Define contamination

Answer 25

process where an object has a radioactive material introduced into it/ on it

Question 26

Name 2 advantages of using contamination

Answer 26

- radioactive isotopes can be used as medical tracers - exposure can be limited with the use of isotopes with a short half-life

Question 27

Name 3 disadvantages of using contamination

Answer 27

- radioactive isotopes may not go where they are wanted - hard to make sure contamination is fully removed - can damage healthy cells

Question 28

What are ways of protecting yourself against contamination?

Answer 28

- using gloves and tongs - wearing protective suits

Question 29

What are the main sources of background radiation?

Answer 29

- radon gas from rocks (granite) - cosmic - building materials - air

Question 30

Define nuclear fission

Answer 30

the splitting of 1 large nucleus to produce 2 smaller ones - 2 or 3 neutrons are also released in the process

Question 31

Describe how nuclear fission works

Answer 31

- a neutron is absorbed into a nucleus (uranium), causing it to be unstable - the nucleus splits into 2 daughter nuclei and 2 or 3 neutrons - the neutrons may collide with another nucleus and cause further fission reactions (chain reaction)

Question 32

Where does nuclear fusion occur naturally?

Answer 32

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