P6

Question 1

What are atomic nuclei made of?

Answer 1

Protons and neutrons.

Question 2

What is the relative charge of a proton?

Answer 2

+1.

Question 3

What is the charge of a neutron?

Answer 3

0 (no charge).

Question 4

What is the overall charge of the nucleus?

Answer 4

Positive, due to protons.

Question 5

What are isotopes?

Answer 5

Atoms of the same element with different numbers of neutrons

Question 6

What remains the same in all isotopes of an element?

Answer 6

The atomic number (protons).

Question 7

What differs between isotopes?

Answer 7

The mass number (due to different numbers of neutrons).

Question 8

Give an example of isotopes.

Answer 8

Carbon-12, Carbon-13, Carbon-14.

Question 9

In nuclear notation, what does A represent?

Answer 9

Mass number = protons + neutrons.

Question 10

What does Z represent?

Answer 10

Atomic number = number of protons (defines the element).

Question 11

What does X represent?

Answer 11

The chemical symbol of the element.

Question 12

What is the charge N in a nuclear symbol?

Answer 12

• If there are N more electrons than protons, the charge is –N.

• If there are N fewer electrons, the charge is +N.

Question 13

What is the defining feature of an element?

Answer 13

The number of protons — it is fixed for each element.

Question 14

Why are some nuclei unstable?

Answer 14

They have too many protons or neutrons, or excess energy.

Question 15

What happens to unstable nuclei?

Answer 15

They undergo radioactive decay to become more stable.

Question 16

Is radioactive decay predictable?

Answer 16

No — it is completely random. You cannot predict when a specific nucleus will decay.

Question 17

What is alpha decay?

Answer 17

Emission of an alpha particle (2 protons + 2 neutrons = helium nucleus). Happens when nucleus is too large.

Question 18

What is beta decay?

Answer 18

A neutron turns into a proton, and an electron (beta particle) is emitted. Happens when there are too many neutrons.

Question 19

What is electron capture?

Answer 19

The nucleus absorbs a neutron and emits a neutron. Happens when the nucleus is too large.

Question 20

What is gamma emission?

Answer 20

Emission of a gamma ray when the nucleus has too much energy.

Question 21

Do gamma emissions change proton or neutron number?

Answer 21

No — they only release energy, not particles.

Question 22

What is a nuclear equation?

Answer 22

A way of representing radioactive decay by showing the changes to the atomic and mass numbers.

Question 23

What happens to atomic and mass number in alpha decay?

Answer 23

• Atomic number: –2

• Mass number: –4

(The nucleus loses 2 protons and 2 neutrons)

Question 24

Example of alpha decay equation:

Answer 24

Pu 239/94 —> U 235/92 + He 4/2

Question 25

What happens to atomic and mass number in beta decay?

Answer 25

• Atomic number: +1 (neutron becomes a proton) • Mass number: stays the same

Question 26

Example of beta decay equation:

Answer 26

C 14/6 —> N 14/7 + e 0/-1

Question 27

What happens to atomic and mass number in gamma decay?

Answer 27

• No change in atomic or mass number • Only energy is released

Question 28

What is ionisation?

Answer 28

The process where radiation knocks electrons off atoms, turning them into ions.

Question 29

What makes a radiation more ionising?

Answer 29

If it collides easily with atoms and has more mass/charge.

Question 30

What is the most ionising type of radiation?

Answer 30

Alpha — but it has low penetration.

Question 31

What stops alpha radiation?

Answer 31

A few cm of air or paper.

Question 32

What is the penetration level of beta radiation?

Answer 32

Medium — it can pass through air but is stopped by 5 mm of aluminium.

Question 33

What is the penetration level of gamma radiation?

Answer 33

High — it passes through most materials and requires thick lead or concrete to reduce it.

Question 34

What is the most penetrating type of radiation?

Answer 34

Gamma rays.

Question 35

What is half-life?

Answer 35

The time it takes for half the radioactive nuclei in a sample to decay.

Question 36

What else can half-life mean?

Answer 36

The time for the count rate or activity to fall by half.

Question 37

Is half-life affected by external conditions?

Answer 37

No — it’s constant and not affected by temperature or pressure.

Question 38

What is activity?

Answer 38

The rate of decay of radioactive nuclei, measured in Becquerels (Bq).

Question 39

What is count rate?

Answer 39

The number of decays detected per second by a Geiger-Müller tube.

Question 40

What is irradiation?

Answer 40

Exposure to radiation from a radioactive source.

Question 41

What is contamination?

Answer 41

Radioactive particles getting on or inside an object.

Question 42

What’s the difference between contamination and irradiation?

Answer 42

• Contamination: radioactive material is present • Irradiation: exposed to radiation, not particles

Question 43

How can contamination occur?

Answer 43

Touching or inhaling radioactive material.

Question 44

Which is more dangerous: contamination or irradiation?

Answer 44

Contamination, because the source remains inside the body.

Question 45

What type of radiation is used in smoke alarms?

Answer 45

Alpha radiation — it ionises air, which is interrupted by smoke.

Question 46

What is gamma radiation used for in medicine?

Answer 46

• Sterilising equipment • Medical tracers • Cancer treatment

Question 47

Why is beta used to measure thickness (e.g. paper)?

Answer 47

It partially penetrates, so changes in count rate reflect thickness.

Question 48

How do we stay safe when using radioactive sources?

Answer 48

• Use lead-lined containers • Tongs to handle sources • Limit exposure time • Increase distance

Question 49

What is nuclear fission?

Answer 49

The splitting of a large unstable nucleus into two smaller nuclei + neutrons + energy.

Question 50

What triggers nuclear fission?

Answer 50

Absorption of a neutron.

Question 51

What does fission release?

Answer 51

• 2–3 neutrons • Kinetic energy • Gamma radiation

Question 52

What is a chain reaction?

Answer 52

The neutrons released go on to cause more fission events.

Question 53

What is nuclear fusion?

Answer 53

Two small nuclei join to form a larger nucleus, releasing lots of energy.

Question 54

Why is fusion difficult on Earth?

Answer 54

Nuclei repel each other due to positive charge — requires extremely high temperature and pressure.

Question 55

Where does fusion naturally occur?

Answer 55

In stars, including the Sun.

Question 56

What makes fusion safer than fission?

Answer 56

It doesn’t produce long-lived radioactive waste and can’t go out of control.

Question 57

What happens when electrons absorb or emit radiation?

Answer 57

• Absorb: Electrons gain energy and move to a higher level. • Emit: They drop back and release energy as EM radiation. • Ionisation occurs if outer electrons are lost.

Question 58

What types of radiation can atomic changes produce?

Answer 58

They can produce radiation from across the EM spectrum, including gamma rays.

Question 59

How do you calculate net decline from radioactive decay?

Answer 59

Use half-life graphs to find how many half-lives have passed, then apply remaining amount = (1/2)^n n is number of half lives

Question 60

What’s the difference between irradiation and contamination?

Answer 60

• Irradiation = exposed to radiation • Contamination = radioactive material on/in the object Contamination is more dangerous long-term.

Question 61

How does half-life affect radiation hazard?

Answer 61

• Short half-life = intense, short-lived risk • Long half-life = low-level but persistent hazard

Question 62

What are uses of radiation in medicine?

Answer 62

• Internal imaging (tracers) • Controlling tumours • Sterilisation All use carefully selected isotopes.