Radioactivity

Question 1

Nucleus

Answer 1

The very small and dense part of an atom, which contains protons and neutrons

Question 2

Proton

Answer 2

A tiny positive particle found inside the nucleus of an atom

Question 3

Neutron

Answer 3

A dense particle found in the nucleus of an atom. It is electrically neutral, carrying no charge

Question 4

Electron

Answer 4

A tiny particle with a negative charge. Electrons orbit the nucleus in atoms or ions

Question 5

Alpha radiation

Answer 5

Alpha particles, each composed of two protons and two neutrons, emitted by unstable nuclei

Question 6

Gamma radiation

Answer 6

Electromagnetic radiation emitted from unstable nuclei in radioactive substances

Question 6

Alpha (α) decay

Answer 6

The nucleus loses 2 protons and 2 neutrons, which are emitted as an α particle

Question 7

Beta (ß) decay

Answer 7

A neutron in the nucleus changes into a proton and an electron - the electron is instantly emitted

Question 8

Isotope

Answer 8

Isotopes of an element are atoms with the same number of protons but different numbers of neutrons. Therefore they have the same atomic number but different mass numbers

Question 9

Ionisation

Answer 9

Any process in which atoms become charged

Question 10

Tracers

Answer 10

A small amount of a radioactive substance used to give information about a mechanical or biological system

Question 11

Radioactive dating

Answer 11

The use of a radioactive substance to give information about the age of an object

Question 12

Carbon dating

Answer 12

A type of radioactive dating used to fine the age of organic materials

Question 13

Uranium dating

Answer 13

A type of radioactive dating used to find the age of igneous rocks

Question 14

What is a radioactive substance?

Answer 14

A radioactive substance contains unstable nuclei that become stable by emitting radiation

Question 15

What types of radiation are given out from a radioactive substance?

Answer 15

Alpha, beta and gamma radiation

Question 16

When does a radioactive source give out radiation?

Answer 16

Radioactive decay is a random event - we cannot predict or influence when it will happen

Question 17

Where does background radiation come form?

Answer 17

Background radiation is from radioactive substances in the environment or from space or from devices such as X-ray machines

Question 18

How was the nuclear model of the atom established?

Answer 18

Rutherford used the measurements from alpha-scattering experiments to prove that an atom has a small positively charged central nucleus where most of the mass of the atom is located

Question 19

Why was the plum pudding model of the atom rejected?

Answer 19

The plum pudding model could not explain why some alpha particles were scattered through large angles

Question 20

Why was the nuclear model accepted?

Answer 20

The nuclear model of the atom correctly explained why the alpha particles are scattered and why some are scattered through large angles

Question 21

How does the nucleus of an atom change when it emits an alpha particle?

Answer 21

The nucleus loses 2 protons and 2 neutrons, which are emitted as an α particle

Question 22

How does the nucleus of an atom change when it emits a beta particle?

Answer 22

A neutron in the nucleus changes into a proton, creating an electron which is instantly emitted

Question 23

What are the properties of alpha radiation?

Answer 23

α radiation of stopped by paper, has a range of a few centimeters in air and consists of particles, each composed of two protons and two neutrons

Question 24

What are the properties of beta radiation?

Answer 24

ß radiation is stopped by thin metal, has a range of about a metre in air and consists of fast-moving electrons emitted from the nucleus

Question 25

What are the properties of gamma radiation?

Answer 25

Ɣ-radiation is stopped by thick lead, has an unlimited range in air and consists of electromagnetic radiation

Question 26

How can we separate a beam of alpha, beta and gamma radiation?

Answer 26

A magnetic or electric field can be used to to separate a beam of alpha, beta and gamma radiation. α-radiation is deflected in one direction, ß-radiation in the opposite direction. Ɣ-radiation and neutrons are undeflected by the magnetic radiation

Question 27

What is alpha, beta and gamma radiation dangerous?

Answer 27

Alpha, beta and gamma radiation ionise substances the pass through. Ionisation in a living cell can damage or kill the cell

Question 28

What do we mean by the “half-life” of a radioactive source?

Answer 28

The half-life of a radioactive isotope is the average time it takes for the number of nuclei of the isotope in sample to halve

Question 29

What do we mean by the activity of a radioactive source?

Answer 29

The activity of a radioactive source is the number of nuclei that decay per second

Question 30

What happens to the activity of a radioactive isotope as it decays?

Answer 30

The number of atoms of a radioactive isotope and the activity both decrease by half every half-life

Question 31

How do we chose a radioactive isotope for a particular job?

Answer 31

The use we can make of a radioactive isotope depends on its half life and the type of radiation it gives out

Question 32

How can we use radioactivity for monitoring?

Answer 32

We can use a radioactive to measure the thickness of foil by measuring the amount of radiation passing through it. The isotope should have a long half-life

Question 33

What are radioactive tracers?

Answer 33

Radioactive tracers are used to trace the flow of a substance through a system. They should be ß or Ɣ emitters that last long enough to monitor but not long enough to cause damage to the body

Question 34

What do we need for radioactive dating?

Answer 34

For radioactive dating of a sample, we need a radioactive isotope that is present in the sample which has a half-life about the same as the age of the sample