Radioactivity

Question 1

Define a radioactive substance

Answer 1

A radioactive substance releases nuclear radiation which is a type of ionising radiation emitted from matters with an unstable nucleus

Question 2

Why are nuclei unstable

Answer 2

If they have an unequal number of protons and neutrons

Question 3

What are isotypes

Answer 3

Atoms of the same element with different numbers of neutrons

Question 4

What are the three types of radiation?

Answer 4

Alpha, beta, and gamma

Question 5

What is the nature of radioactive decay

Answer 5

It is completely random

Question 6

Can we predict the decay of a specific individual atom?

Answer 6

No, but we can estimate the half life of a large group of them

Question 7

Define half life

Answer 7

The time it takes for the number of nuclei to halve, or for the count rate of radioactive radiation to halve

Question 8

Note some uses for radioactive materials

Answer 8

• Measuring thickness
• Sterilisation
• Smoke alarms
• Cancer treatment
• Carbon dating

Question 9

What is the meaning of the atomic number and mass number?

Answer 9

Atomic numbers are unique to each element, and is equal to the number of protons present in the nucleus. The mass number is the sum of protons and neutrons. The mass number goes higher.

Question 10

What do isotopes have

Answer 10

Different mass numbers

Question 11

What is an alpha particle equal to

Answer 11

A helium nucleus: two protons and two neutrons

Question 12

How can equations for alpha decay be written

Answer 12

Basically using the adjusted Helium symbol (He2+), and making sure that all of the bits on the top and bottom add up at the end.

Question 13

Describe alpha radiation

Answer 13

Slowly moving and strongly ionising. It has little penetrating power, and it’s range is apparently -5cm. It can be stopped by thin paper.

Question 14

What is beta radiation

Answer 14

The equivalent of a high energy electron

Question 15

What is the charge and mass of beta radiation

Answer 15

-1 charge and a negligible mass

Question 16

What represents Beta?

Answer 16

A ß thingy always with a 0 on top and -1 at its base

Question 17

How quickly does beta move and how ionising is it

Answer 17

It is faster moving but less strongly ionising. Its range is up to one metre, and it can be absorbed by thin metal

Question 18

What is gamma radiation

Answer 18

Not a particle but a type of electromagnetic radiation. It is a wave, meaning that it has no mass or charge

Question 19

How quickly does gamma travel and how ionising is it

Answer 19

At the speed of light, but it is only weakly ionising

Question 20

What is required to absorb gamma

Answer 20

A thick lead block

Question 21

List some natural sources of radiation

Answer 21

Cosmic rays, rocks and even living things

Question 22

List some man made sources of radiation

Answer 22

X-Rays, nuclear power stations, nuclear weapons

Question 23

What is the difference between fission and fusion?

Answer 23

Fission breaks atoms apart and fusion brings them together

Question 24

What happens in fission

Answer 24

One single neutron starts the reaction, in turn releasing 2 or 3. In the correct environment, these can go on to release yet more.

Question 25

How do we prevent chain reactions from getting out of control

Answer 25

Control rods are key, absorbing 2 out of every 3 electrons released in every reaction. The moderator also slows the neutrons released to ensure they can be absorbed by uranium nuclei, to cause another reaction

Question 26

What does the concrete shield do

Answer 26

It ensures that no radiation escapes

Question 27

What fuels nuclear reactions

Answer 27

Uranium

Question 28

What slows neutrons

Answer 28

The graphite moderator

Question 29

What will be the fuel for fusion

Answer 29

Deuterium

Question 30

What conditions would be needed for successful fusion

Answer 30

High temperature and pressure