P1 Atomic Structure

Question 1

What do you call nuclei that give out radiation?

Answer 1

Unstable nuclei

Question 2

Define the activity of a radioactive source.

Answer 2

The rate at which it decays

Question 3

What is the activity measured in?

Answer 3

becquerels (Bq)

Question 4

What is one becquerel equivalent to?

Answer 4

One decay per second

Question 5

What material stops alpha radiation?

Answer 5

A few centimetres of air or paper

Alpha is lowly penetrating and highly ionising

Question 6

What material stops beta radiation?

Answer 6

A few milimetres of aluminium

Beta is medium penetrating and medium ionsising.

Question 7

What material stops gamma radiation?

Answer 7

Many centimetres of lead or metres of concrete

Gamma is highly penetrating and lowly ionsising.

Question 8

What is a gamma particle made up of?

Answer 8

Electromagnetic radiation

Question 9

What is an alpha particle made up of?

Answer 9

Two neutrons and two protons (a helium nucleus)

Question 10

What is a beta particle made up of?

Answer 10

A high-speed electron from where a neutron has turned into a proton.

Question 11

What is the fourth type of nuclear radiation?

Answer 11

A neutron (n)

Question 12

Define Radioactive contamination.

Answer 12

The unwanted presence of radioactive material on another object/thing and it becomes radioactive.

Question 13

What is irradiation?

Answer 13

The process of exposing an object to nuclear radiation where it doesn’t become radioactive itself.

Question 14

Name 3 different ways to protect against unwanted irradiation.

Answer 14

• using sources of the lowest activity possible
• wearing protective clothing
• not handling sources with bare hands

Question 15

What is the half-life of a radioactive isotope?

Answer 15

The average time it takes for half the nuclei to decay / time for the count rate to fall to 50% of its original value.

Question 16

Define count rate.

Answer 16

The number of decay recorded each second by a detector.

Question 17

Name 2 facts about isotopes with a short half-life.

Answer 17

• They are very unstable, so exposure can be very hazardous
• They do not remain radioactive for long

Question 18

Name 2 facts about isotopes with a long half-life.

Answer 18

• They are more stable, so they aren’t radioactive for long
• Exposure is less hazardous as radiation is emitted very slowly.

Question 19

How is nuclear radiation used in medical tracers?

Answer 19

• The radioactive isotope is ingested or injected into the body.
• It can be detected outside of the body due to the high penetration power.

Question 20

Name 2 specific uses of radioactive isotopes used as medical tracers.

Answer 20

• To monitor kidney function: if it builds up in a kidney it could indicate that one isn’t functioning efficiently.
• To locate damage or blockages in intestines: radioactivity can’t be detected if there’s a blockage, and if there’s damage to the intestines, it passes out into other areas of the body.

Question 21

What must be considered when choosing which isotope to use for a specific job?

Answer 21

The half-life, penetration power, and how ionising it is.
e.g. medical uses require something with a short half-life and low ionising power, but a smoke detector would require something with a longer half-life and high ionising, but lowly penetrating.

Question 22

What must be done to properly evaluate any new risks from new studies?

Answer 22

It must be peer reviewed and tested through experiment to prove that the results are reproducible.

Question 23

What factors affect the level of background radiation that somebody experiences?

Answer 23

Their location and occupation

Question 24

What percentage of radiation is from natural sources?

Answer 24

87%
(includes from: radon gas, food, gamma rays, and cosmic rays)

Question 25

Define nuclear fission.

Answer 25

The splitting of a large unstable nucleus through absorbing a neutron.

Question 26

What is emitted as a result of nuclear fission?

Answer 26

• 2 smaller nuclei of roughly equal size
• 2 or 3 neutrons
• gamma rays
• energy

Question 27

How does the chain reaction form?

Answer 27

All of the products have kinetic energy so they move and get absorbed by other large unstable nuclei, creating a chain reaction.

Question 28

What is this chain reaction like in a nuclear reactor?

Answer 28

It is controlled to give a constant, steady release of energy, they use graphite rods to absorb the unwanted neutrons.

Question 29

What is the chain reaction like in nuclear weapons?

Answer 29

Nuclear weapons are the result of uncontrolled chain reactions

Question 30

Define nuclear fusion.

Answer 30

The joining of two smaller nuclei to form a larger nucleus.

Question 31

What is emitted from nuclear fusion?

Answer 31

• Some of the mass is converted into energy
• Some of the energy can be emitted as radiation

Question 32

What conditions must be met for nuclear fusion?

Answer 32

Very high temperatures and pressures to overcome the electrostatic repulsion so that the positive nuclei can be close enough for fusion to take place.

Question 33

What particle is represented by He^4,2?

Answer 33

Alpha

Question 34

What particle is represented by e^0,-1

Answer 34

Beta

Question 35

How much do each of the radiation particles reduce the mass number by if emitted?

Answer 35

alpha = -4
beta = 0
gamma = 0

Question 36

How much do each of the radiation particle reduce the atomic number by if emitted?

Answer 36

Alpha = -2
beta = +1
gamma = 0