CP6

Question 1

What are the three types of radiation?

Answer 1

1. Alpha
2. Beta
3. Gamma

Question 2

What is half-life?

Answer 2

The average time taken for half of the radioactive nuclei in a sample of radioactive material to have decayed.

Question 3

Who discovered that atoms contained subatomic particles and when?

Answer 3

J.J Thomson discovered this in 1897 by carrying out various experiments.

Question 4

What is the plum pudding model?

Answer 4

This is a model for atoms that explains the evidence of subatomic particles. The model had pudding with plums scattered throughout it. The pudding represented the positively charged material, with the plums representing negatively charged electrons throughout it.

Question 5

What was the gold foil experiment?

Answer 5

Rutherford got a piece of gold foil and shined a laser of alpha particles at the gold foil. Rutherford observed that most alpha particles (rays) went straight through the foil however some alpha particles (rays) deflected off into different directions and some even bounced back. From this, Rutherford was able to conclude that an atom had mostly empty space, however the mass of all of the atom was in the center (nucleus) of the atom.

Question 6

What is the radius of a nucleus?

Answer 6

1 x 10⁻¹⁵

Question 7

What is the radius of an atom?

Answer 7

1 x 10⁻¹⁰

Question 8

Where is most of the mass of an atom concentrated?

Answer 8

Most of the mass of an atom is concentrated in its nucleus.

Question 9

What is the relative charge of a proton?

Answer 9

+1

Question 10

What is the relative charge of a neutron?

Answer 10

0

Question 11

What is the relative charge of an electron?

Answer 11

-1

Question 12

What is the relative mass of a proton?

Answer 12

1

Question 13

What is the relative mass of a neutron?

Answer 13

1

Question 14

What is the relative mass of an electron?

Answer 14

1/1835

Question 15

How are the number of protons and number of electrons linked?

Answer 15

The number of protons is equal to the number of electrons.

Question 16

What does the atomic mass represent in terms of subatomic particles?

Answer 16

The atomic mass represents the number of protons and neutrons added together.

Question 17

What does the atomic number represent in terms of subatomic particles?

Answer 17

The atomic number represents the number of protons only.

Question 18

What are isotopes?

Answer 18

Atoms that have the same atomic number, but different atomic mass. This means that they have the same amount of protons as the normal element has however it has a different number of neutrons.

Question 19

What is the emission spectrum?

Answer 19

A set of wavelengths of light or electromagnetic radiation showing which wavelengths have been given out (emitted) by a substance.

Question 20

What is the absorption spectrum?

Answer 20

A spectrum of light (or electromagnetic radiation) that includes black lines. These are caused by some wavelengths being absorbed by the materials that the light (or radiation) passes through.

Question 21

What is ionising radiation?

Answer 21

It is radiation that cause charged particles (ions) to be formed. It can cause tissue damage and DNA mutations.

Question 22

What are some sources of background radiation?

Answer 22

The main source of background radiation is radon gas. Other sources include: Hospital treatments (such as x-rays), cosmic rays etc.

Question 23

How is radon gas produced?

Answer 23

Radon gas is produced by rocks that contain small amounts of uranium. Radon diffuses into the air from rocks and soil and can build up in houses, especially where there is poor ventilation.

Question 24

What does the amount of radon gas depend on?

Answer 24

The amount of radon in the air depends on the type of rock and its uranium content. Rock type and building stone vary around the country and so does the amount of radon.

Question 25

What are cosmic rays?

Answer 25

Charged particles with a high energy that come from stars.

Question 26

How can the radioactivity of a source be measured?

Answer 26

By using a Geiger-Müller (GM) tube.

Question 27

What is a Geiger-Müller (GM) tube and how does it work?

Answer 27

It is a device that can detect ionising radiation and is used to measure the activity of a radioactive source. The GM tube is connected to a counter, and this counter clicks every time radiation is detected. The count rate you get from the GM machine is the amount of clicks per second or minute.

Question 28

What happens to a substance when its nucleus starts to decay?

Answer 28

When decay occurs, radiation is emitted which causes the nucleus to lose energy and become more stable.

Question 29

Can you predict when a nucleus starts to decay?

Answer 29

You cannot predict when a nucleus will decay - it is a random process.

Question 30

What is radioactive decay?

Answer 30

It is when an unstable nucleus changes by giving out ionising radiation to become more stable.

Question 31

What particles get emitted from an unstable nucleus during radioactive decay?

Answer 31

Alpha particles, Beta particles, Positrons, Gamma rays, Neutrons.

Question 32

Describe the penetrating properties of alpha particles?

Answer 32

Alpha particles: will travel a few centimeters in the air, they are very ionising, they can be stopped by a sheet of paper.

Question 33

Describe the penetrating properties of beta particles?

Answer 33

Beta particles: will travel a few metres in the air, they are moderately ionising, they can be stopped by 3mm thick aluminium

Question 34

Describe the penetrating properties of gamma rays?

Answer 34

Gamma rays: will travel a few kilometers in the air, they are weakly ionising, they need thick lead or several metres of concrete to stop them

Question 35

What happens when an unstable nucleus changes and emits particles?

Answer 35

When an unstable nucleus changes and emits particles, the atomic number can change. This makes the atom become a different element.

Question 36

What happens during beta particle decay (β⁻)?

Answer 36

During β⁻ decay, a neutron changes into a proton and an electron. The electron is ejected from the atom. The atomic number is increased by 1 but there is no change to the mass number.

Question 37

What happens during positron decay (β⁺)?

Answer 37

In β⁺ decay, a proton becomes a neutron and a positron. The atomic number goes down by one but the mass number does not change.

Question 38

What happens to the mass number and atomic number of an atom when a neutron is ejected?

Answer 38

If a neutron is ejected from a nucleus, the mass number goes down by 1 but the atomic number doesn't change.

Question 39

When may nuclei lose energy?

Answer 39

Nuclei may also lose energy as gamma radiation when the subatomic particles in the nucleus are rearranged. This helps to make them more stable.

Question 40

What is a nuclear equation?

Answer 40

It is an equation representing a change in atomic nucleus due to radioactive decay. The total mass number must be the same on each side and the total charges must be the same (e.g. Radium 226 emits an alpha particle: ²²⁶Ra₈₈ --> ⁴He₂ + ²²²Ra₈₆)

Question 41

How can you do nuclear equation questions?

Answer 41

*DO NUCLEAR EQUATION QUESTIONS*

Question 42

What can a small amount of ionising radiation over long periods of time do?

Answer 42

This can damage the DNA inside a cell, causing a mutation to occur.

Question 43

How can you handle highly radioactive sources?

Answer 43

The intensity of radiation decreases with distance from the source, so: 1. sources are always handled with tongs. 2. The risk can be reduced by not pointing sources at people 3. The risk can be reduced by storing radioactive material in lead-lining containers

Question 44

When is a person irradiated from radiation?

Answer 44

Someone is irradiated when they are exposed to alpha, beta or gamma radiation from nearby radioactive materials. Once the person moves away, the irradiation stops.

Question 45

When is a person contaminated from radiation?

Answer 45

Someone becomes contaminated if they get particles if radioactive materials under their skin or inside their body. They will be exposed to radiation as the unstable isotopes in the material decay and this will continue until all of the material has decayed or until the source of contamination is removed (which is not always possible). Water and soil can also be contaminated, so contamination can also spread into the food chain.