Topic 11

Question 1

What two processes can cause electrons to change energy levels

Answer 1

• Large heat increase

- The presence of an electrical field

Question 2

What are the four scenarios in which an atom may become unstable

Answer 2

1. The atom having too many neutrons
2. The atom having too few neutrons
3. The atom having too much mass
4. The atom having too much energy

Question 3

How do unstable nuclei become more stable

Answer 3

Unstable nuclei are radioactive, so emit radiation in order to become more stable.
They type of radiation they emit depends on what makes them unstable

Question 4

What are the constituents of an alpha particle

Answer 4

Two protons and two neutrons

Question 5

What are penetration capabilities of alpha radiation

Answer 5

Alpha particles are weakly penetrating and so are stopped by a few centimetres of air or a sheet of paper

Question 6

What does beta-minus radiation consist of

Answer 6

High-energy electrons

Question 7

What does beta-plus radiation consist of

Answer 7

High-energy positrons

Question 8

What are the penetration capabilities of beta-minus radiation

Answer 8

Beta-minus radiation has medium penetrative capabilities and is stopped by a few mm of aluminium or around 1 m of air

Question 9

What are the penetration capabilities of beta-plus radiation

Answer 9

Beta-plus radiation is almost instantaneously annihilated by electrons and so has virtually zero range

Question 10

What is gamma radiation

Answer 10

Gamma radiation is a form of high-energy electromagnetic radiation

Question 11

What charge do gamma rays have

Answer 11

Gamma rays are a form of electromagnetic radiation and so don’t have a charge

Question 12

Which type of radiation is most ionising

Answer 12

Alpha radiation

Question 13

Which type of radiation is most weakly ionsing

Answer 13

Gamma radiation

Question 14

What type of radiation travels the fastest and at what speed

Answer 14

Gamma radiation travels the fastest since it is a type of electromagnetic radiation and so travels at the speed of light

Question 15

Under what circumstance is alpha radiation emitted

Answer 15

When a nucleus has too much mass

Question 16

Under what circumstance is beta-minus radiation emitted

Answer 16

Beta-minus radiation is emitted when a nucleus has too many neutrons

Question 17

Under what circumstance is beta plus radiation emitted

Answer 17

Beta-plus radiation is emitted when a nucleus has too many protons

Question 18

Under what circumstance is gama radiation emitted

Answer 18

Gamma radiation is emitted when a nucleus has too much energy

Question 19

What are the penetrative capabilities of gamma radiation

Answer 19

Gamma radiation is highly penetrative but is absorbed by several inches of lead or several metres of concrete

Question 20

Explain the process of beta-minus decay

Answer 20

Beta-minus decay is where a neutron in the nucleus turns into a proton, and releases an electron and an electron antineutrino

Question 21

Explain the process of beta-plus decay

Answer 21

Beta-plus decay is where a proton in the nucleus turns into a neutron, and releases a position and an electron neutrino

Question 22

How does the mass of a nucleus compare to the sum of the individual masses of it s constituents

Answer 22

The mass of the nucleus is always less the sum of the individual masses of its constituents

Question 23

What is the name given to the difference in the mass of a nucleus and its individual constituents

Answer 23

The mass defect

Question 24

Explain why there is a mass defect in nuclei

Answer 24

The mass defect is a result of some of the mass being converted into energy used to hold the nucleus together

Question 25

What is the name for the value of the energy required to hold a nucleus together

Answer 25

Binding energy

Question 26

How can the mass defect be used to calculte the binding energy of a nucleus

Answer 26

By substituting the mass defect into Einstein's mass energy equation

Question 27

Why isn't it useful to compare binding energies for different nuclei

Answer 27

Different nuclei have different numbers of nucleons

Question 28

What is a more useful measure used to compare the binding energies of different nuclei

Answer 28

The binding energy per nucleon

Question 29

State the equation used to calculate the binding energy per nucleon of a nucleus

Answer 29

Binding energy per nucleon = Binding energy / Number of Nucleons

Question 30

What is the relationship between the stability of a nucleus and its binding energy per nucleon

Answer 30

The larger the binding energy per nucleon, the more stable the nucleus will be

Question 31

What is the most stable nucleus

Answer 31

Iron

Question 32

Name two nuclear processes thaat can be used to generate energy

Answer 32

1. Nuclear Fission | 2. Nuclear Fusion

Question 33

What are the two types of fission

Answer 33

1. Spontaneous fission | 2. Induced fission

Question 34

Explain the basic process of induced fission

Answer 34

A large nucleus absorbs a thermal neutron causing it to split into two smaller nuclei, releasing energy and at least one neutron

Question 35

Explain the basic process of nuclear fusion

Answer 35

Two smaller nuclei join together to form a larger one, and releases energy in the process

Question 36

Why is nuclear fusion is not currently a feasible method of energy production

Answer 36

Nuclear fusion requires very high temperatures in order to overcome the electrostatic force between the nuclei. THis makes it hard to contain and means more energy must be inputted to heat the nuclei then is generated

Question 37

Where does nuclear fusion constantly take place

Answer 37

In stars (for example, the sun)