Radioactivity and Particles

Question 1

The atomic notation:

Answer 1

Atomic mass - A

Atomic number - Z

Question 2

The stability of isotopes:

Answer 2

There is a nuclear force holding the protons together in the nucleus. The presence of neutrons affects the balance between the repulsion and nuclear forces. Too many or too few neutrons would make the nucleus unstable which will eventually decay by emitting ionizing radiation

Question 3

Properties of alpha radiation:

Answer 3

• Fast-moving particles
• Helium nuclei
• Large mass
• Charge: +2
• Low penetrating power
• High ionizing power

Question 4

Properties of beta radiation:

Answer 4

• Fast-moving electrons
• Light (mass)
• Charge: -1
• More penetrating power
• Less ionizing power

Question 5

Properties of gamma radiation:

Answer 5

• Electromagnetic wave
• No mass and no charge
• Photons
• Most penetrating
• Least ionizing

Question 6

The symbol used for neutron in radioactive decay:

Answer 6

¹n₀

Question 7

The speciality of neutron emission:

Answer 7

It can be absorbed by other atoms and makes them radioactive

Question 8

Changes in alpha decay:

Answer 8

Mass no. decreases by 4

Atomic no. decreases by 2

Question 9

Changes in beta decay:

Answer 9

Mass no. doesn’t change

Atomic no. goes up by one

Question 10

Changes in neutron emission:

Answer 10

Mass no. goes down by one

Atomic no. doesn’t change

Question 11

Unit of radioactivity:

Answer 11

Bq

Question 12

What is Becquerel?

Answer 12

A measure of how many unstable nuclei are disintegrating per second

Question 13

Set up of GM tube:

Answer 13

Mica sheet
Glass tube
Conducting surface
Central electrode connected to a detecting circuit: a counting circuit or a rate meter (loudspeaker)

Question 14

Sources of background radiation:

Answer 14

• Radioactive rocks: radon gas
• Cosmic rays from exploding stars and Sun
• Living things: C-14
• Nuclear power stations, nuclear weapons
• Medical use eg. tracers

Question 15

What is the relationship between the decay and the no. of nuclei?

Answer 15

The rate of decay falls as time passes because there are fewer nuclei to decay

Question 16

Advantages of gamma radiography over X-rays:

Answer 16

• Gamma source can be in small amounts
• Don’t require a power source
• Don’t require large equipment

Question 17

Advantages of gauging using radioactive isotopes:

Answer 17

• No contact with the material being gauged

- Coal dust can cause false readings with optical gauging systems

Question 18

A decay product of radium:

Answer 18

Radon gas

Question 19

Example of alpha emitter:

Answer 19

Radon gas

Question 20

Ways of detecting ionizing radiation?

Answer 20

GM tube
Photographic film
Badges using the thermoluminescence property

Question 21

What is thermoluminescence?

Answer 21

Thermoluminescence means that the exposed material will give out light when it becomes hot

Question 22

Safe handling of radioactive materials:

Answer 22

• Lead-lined boxes
• Labelled as hazardous
• Placed in a metal cabinet
• Use tongs
• Hold away from your body
• Spent uranium fuel rods from nuclear reactors are stored underwater until neutron radiation levels drop to a safe level

Question 23

Use of carbon dating:

Answer 23

To find the age of organic matter

Question 24

Limitations on carbon dating:

Answer 24

• It assumes the levels of cosmic rays reaching the Earth to be constant, which can
  be inaccurate
• Can’t be used to date samples older than 50,000 to 60,000 years because after 10 years the sample because the amount of C-14 becomes too small to measure accurately

Question 25

What is a nuclear transformation?

Answer 25

Turn elements into different isotopes

Question 26

How is C-14 formed in the air?

Answer 26

The cosmic rays from space are continuously bombarding the Earth’s atmosphere. When it hits the atoms of gas in the atmosphere, it causes the nuclei of the atoms to break. The parts fly off at high speed. When the fast-moving neutrons hit the nitrogen atoms it transforms it into a C-14 atom.

Question 27

The half-life of the C-14 atom is _________

Answer 27

5600 years

Question 28

What is nuclear fission and fusion?

Answer 28

Fission: Heavier atoms are split into lighter atoms and a neutron along with large amounts of energy

Fusion: Lighter atoms are forced to join together to form heavier atoms and a neutron along with large amounts of energy

Question 29

Elements present within the core of the Earth:

Answer 29

Uranium
Thorium
Potassium

Question 30

Advantages of nuclear fusion

Answer 30

Reactants are more readily available

Do not produce radioactive waste

Question 31

Fuel for a nuclear fission reactor

Answer 31

U-235

Question 32

Why is U-235 a fissile material?

Answer 32

Because its nucleus can be split easily

Question 33

Products of the decay of U-235:

Answer 33

Krypton-89 and Barium-144

Question 34

What is a chain reaction?

Answer 34

A series of reaction that occurs when neutron from each fission is absorbed by the surrounding nuclei

Question 35

A requirement for a chain reaction:

Answer 35

Critical mass: the minimum mass of fuel

Question 36

Set up and uses of nuclear reactors:

Answer 36

Fuel rods of enriched uranium

Moderator (graphite or water): absorbs the kinetic energy of neutrons

Control rods (boron or cadmium): absorb neutrons and take them out of the fission reaction

Steel vessel surrounded with thick concrete

Question 37

The disadvantage of fission reactions:

Answer 37

The storage of radioactive elements with long half-lives causes long-term storage problems. They have to be sealed in containers and stored underground

Question 38

The advantage of fission reactions:

Answer 38

Do not produce carbon dioxide or acidic gases

Do not contribute to global warming and acid rain

Only small amounts of fuel are needed to start a chain reaction