Radioactivity

Question 1

What is the activity of an unstable nucleus?

Answer 1

Activity I’d the rate at which a source of unstable nuclei decays

Question 2

What is the unit of radioactive activity?

Answer 2

Becquerel

Question 3

What is count-rate?

Answer 3

The number of radioactive decays per second for a radioactive source

Question 4

What is an example of a detected that may be used to measure count-rate?

Answer 4

Geiger-muller tube

Question 5

What is the nature of radioactive decay like?

Answer 5

Random, which nuclei decays and when is determined only by chance and it’s impossible to predict which nuclei will decay and when

Question 6

What is a half-life of a radioactive isotope?

Answer 6

The time it takes for the number of unstable nuclei in a substance to halve and the time it takes for the count rate from a sample to fall to half its initial level

Question 7

What are the advantages of nuclear power for generating electricity?

Answer 7

Nuclear fuels don’t produce carbon dioxide, the fuel is readily available so would reduce strain on the fossil fuel supplies, less nuclear fuel has to be used to produce the same amount of energy as burning fossil and doesn’t contribute to global warming

Question 8

What are some disadvantages of using nuclear power to generate electricity?

Answer 8

Unpopular - public perceive nuclear power as very dangerous, security risks as the radioactive substances can be useful for terrorists, expensive to commission and decommission the stations and risk of nuclear accidents

Question 9

What is nuclear fission?

Answer 9

The splitting of large, unstable nuclei to form smaller more stable nuclei

Question 10

What usually needs to happen to induce fission?

Answer 10

The unstable nuclei must absorb a neutron and spontaneous fission

Question 11

What is emitted in a fission reaction?

Answer 11

Two smaller nuclei, two or three neutrons, gamma rays and energy

Question 12

What is the name of common fissile nuclei?

Answer 12

Uranium-235

Question 13

What are the three main components of the core a nuclear reactor?

Answer 13

Moderator, fuel and control rods

Question 14

What takes place during a chain reaction in a nuclear reactor?

Answer 14

An unstable nucleus absorbs a neutron, the nucleus undergoes fission releases 2 or 3 further neutrons and these induce more fission which results in a chain reaction

Question 15

What is the consequence of an uncontrolled chain reaction?

Answer 15

The rate of fission events become to high and results in the production of too much energy and this can lead to a nuclear explosion

Question 16

How is the chain reaction in a fission reactor kept under control?

Answer 16

Control rods are positioned in between the fuel rods, the rate of fission is controlled by moving these rods up and down and the lower the rods are inserted, the slower the rate of fission

Question 17

What is the role of the moderator in a nuclear reactor?

Answer 17

To slow down the neutron so they are travelling at speeds which allowing them to be absorbed by fissile nuclei and cause fission

Question 18

How is electricity produced in a nuclear power station?

Answer 18

The reactions release thermal energy, the thermal energy is used to boil water and then produce steam and this steam is then used to turn a turbine which starts the generator

Question 19

What is nuclear fusion?

Answer 19

When two light nuclei join to produce a heavier nucleus and release energy

Question 20

What are the name of isotopes of hydrogen which are commonly used in nuclear?

Answer 20

Deuterium and tritium

Question 21

Which releases more energy, nuclear fusion or fission?

Answer 21

Nuclear fusion

Question 22

What is the difficulty of generating energy through nuclear fusion?

Answer 22

Fusion requires very high temperatures which in itself requires large quantities of energy, currently the production of fusion results in a net loss of energy

Question 23

What is an example of where fusion occurs?

Answer 23

In the sun (stars use fusion as their energy source)

Question 24

Why does nuclear fusion require so much energy?

Answer 24

Both nuclei are positive therefore a lot of energy is required to overcome the electrostatic repulsion between the two nuclei

Question 25

What are the four types of nuclear radiation?

Answer 25

Alpha and beta particles, gamma rays and neutrons

Question 26

What is meant by background radiation?

Answer 26

Radiation that is always present and it’s in very small amounts and so not harmful

Question 27

What are sources of background radiation?

Answer 27

Rocks, cosmic rays from rays, nuclear weapons testing and nuclear accidents

Question 28

How do you measure and detect background radiation?

Answer 28

Photographic film and Geiger-Müller counter

Question 29

How is photographic film used to measure radiation?

Answer 29

A photographic film turns dark when it absorbs radiation, this is useful for people who work on radiation as the more radiation they are exposed to, the darker the film becomes therefore the workers know when they have been exposed to too much radiation

Question 30

How is Geiger-Muller tubes used to measure radiation?

Answer 30

When the Geiger-Muller tube absorbs radiation it produces a pulse, which a machine uses to count the amount of radiation, the frequency of the pulse depends on how much radiation is present, a high frequency would mean the tube is absorbing a large amount of radiation

Question 31

What constitutes an alpha particle?

Answer 31

Two protons and neutrons and it’s the same as a helium nucleus

Question 32

What is the range of an alpha particle?

Answer 32

A few centimetres

Question 33

What is block beta radiation?

Answer 33

A thin sheet of aluminium and several metres of air

Question 34

What will Bloch gamma radiation?

Answer 34

Several centimetres of lead and few metres of concrete

Question 35

Which type of radiation is most ionising?

Answer 35

Alpha radiation

Question 36

Which type of radiation is least ionising?

Answer 36

Gamma radiation

Question 37

How does gamma emission affect mass/charge of an atom?

Answer 37

Both mass and charge remain unchanged

Question 38

What is the plum-pudding model of the atom?

Answer 38

A sphere of positive charge, with the negatively charged electrons distributed evenly throughout it

Question 39

Prior to the discovery of the electron, what was believed about the atom?

Answer 39

believed to be indivisible

Question 40

Which experiment led to the plum-pudding model being discarded?

Answer 40

Rutherfords alpha-scattering experiment

Question 41

What is the name given to the currently accepted model model of the atom?

Answer 41

The Bohr model

Question 42

What is Rutherfords experiment like?

Answer 42

Alpha particles were fired at a thin sheet of gold foil, most particles went straight through, some particles were deflected by small angles and few particles were deflected by large angles

Question 43

What are the conclusions of Rutherfords experiment?

Answer 43

Most of the atom is empty space, the nucleus has a positive charge and most of the mass is concentrated in the nucleus

Question 44

What happens in the process of beta plus decay?

Answer 44

A proton turns into a neutron and a positron

Question 45

What is the process called when a neutron changes into a proton and an electron?

Answer 45

Beta minus decay

Question 46

When alpha decay occurs, what happens to the atomic number and the mass number of the atom?

Answer 46

The atomic number decreases by 2, the mass number decreases by 4 and new element is made since the atomic number has changed

Question 47

What effect does beta minus decay have on the mass number and atomic number of an atom?

Answer 47

The mass number stays the same as the total number of neutrons and protons hasn’t changed and the atomic number increases since there is one more proton

Question 48

What is the approximate radius of an atom?

Answer 48

1x10^-10 metres

Question 49

What are the three subatomic constituents of an atom?

Answer 49

Protons, neutrons and electrons

Question 50

Where is most of the mass of an atom concentrated?

Answer 50

In the nucleus

Question 51

Approximately what proportion of the total radius of an atom is the radius of the nucleus?

Answer 51

1/10,000

Question 52

What are the arrangements of the subatomic particles?

Answer 52

Protons and neutrons are found in the atom’s nucleus and electrons are found in discrete energy levels around the nucleus

Question 53

What type of charge does the nucleus of an atom have?

Answer 53

Positive charge

Question 54

What two ways can an atoms electron arrangement can be changed?

Answer 54

Absorbing or emitting EM radiation

Question 55

How can an atoms electron arrive change when it absorb EM radiation?

Answer 55

Electrons move to higher energy levels and they move away from the nucleus

Question 56

How can atoms electron arrangement change when it emits EM radiation?

Answer 56

Electrons move to a lower energy level and they move towards the nucleus

Question 57

How does the ratio of electrons to protons in an atom result in the atom having no overall charge?

Answer 57

The number of protons is equal to the number of electrons and they have equal and opposite charges so charge cancels

Question 58

What do all forms of the same element have in common?

Answer 58

Number of protons

Question 59

What is an isotope of an atom?

Answer 59

same number of protons but different number of neutrons

Question 60

What property differs between isotopes of an atom?

Answer 60

The mass of an atom

Question 61

How do atoms Turks into positive ions?

Answer 61

The lose one or more of their outer electrons and electrons are negatively charged so the resultant charge of the atom is positive