P7 - Radioactivity - Complete

Question 1

Why do radioactive substances emit radiation?

Answer 1

In order to stabilise their nuclei

Question 2

What is the most penetrating type of radiation?

Answer 2

Gamma radiation

Question 3

What particle did Ernest Rutherford fire at foil o discover the idea of positive nuclei?

Answer 3

Alpha particles

Question 4

What charge is alpha radiation?

Answer 4

Positive

Question 5

What is radioactive decay and when does is happen?

Answer 5

Radioactive decay is when a radioactive substance’s nucleus emits radiation in order to become stable, it is a random even that occurs without stimulation to the nucleus

Question 6

What are the three main types of radiation?

Answer 6

Alpha, beta and gamma

Question 7

Why was the experiment to fire alpha particles at the metal foil in a vacuum chamber?

Answer 7

Because otherwise the air particles would absorb the radiation

Question 8

Why could the plum pudding model still not make sense after Rutherford’s experiments?

Answer 8

As it would be impossible for the particles to rebound at the same angles that some of them had if it was true

Question 9

What does and electron moving shell cause?

Answer 9

A small burst of radiation called a photon. This burst is equal to the energy change caused by the jump

Question 10

What changes is alpha decay?

Answer 10

The number of protons and neutrons in the nucleus

Question 11

What changes in beta decay?

Answer 11

The number of protons in the nucleus

Question 12

What is the mass number?

Answer 12

How many protons + neutrons there are in an atom. It is represented by the letter A

Question 13

What is the atomic number?

Answer 13

Otherwise known as the proton number, it is the number of protons in a nucleus. It has the letter Z

Question 14

What is an isotope?

Answer 14

An atom of the same element with a different number of neutrons

Question 15

What makes up an alpha particle?

Answer 15

Two protons and two neutrons. It is identical to the helium nucleus

Question 16

What happens when an unstable nucleus emits an alpha particle?

Answer 16

Its mass number goes down by 4 and its charge decreases by 2

Question 17

What makes up a beta particle and how is it made?

Answer 17

An electron makes it up, and it is created by a neutron separating into an electron and a proton in the atom’s nucleus

Question 18

What happens when an unstable nucleus emits a beta particle?

Answer 18

The atomic number of the nucleus goes up by 1, its mass decreases by 1/2000th, and the charge of the nucleus is increased, as it has gained a new proton

Question 19

What is gamma emission?

Answer 19

Gamma emission is uncharged electromagnetic radiation from the nucleus of an atom. As it has no charge and no mass, it does not change the atom in any way

Question 20

What can cause neutron emission?

Answer 20

Neutron emission can be caused by alpha particles colliding with unstable nuclei - causing them to become even more unstable and so they emit a neutron. Because neutrons are uncharged, they can pass through

Question 21

Why are normal particles not radioactive?

Answer 21

Because the force inside the nucleus, called strong nuclear force, is strong enough to resist the repulsion between the protons and can keep the neutrons from moving away from the nucleus

Question 22

What can stop alpha radiation?

Answer 22

A piece of paper

Question 23

What can stop beta radiation?

Answer 23

An aluminium sheet of about a 5mm thickness, and a lead sheet about 2-3mm thick

Question 24

What can stop gamma radiation?

Answer 24

Concrete that is more than 1m thick and a several cm thick lead sheet

Question 25

What is alpha radiation's range through the air?

Answer 25

About 5cm

Question 26

What is beta radiation's range through the air?

Answer 26

About 1m

Question 27

What is gamma radiation's range through the air?

Answer 27

Unlimited - it can spread out through the air without being absorbed

Question 28

What can radiation do to other atoms?

Answer 28

It can knock their electrons out of orbit: causing them to become charged ions. They are said to have been irradiated

Question 29

What does ionisation do to a living cell?

Answer 29

It can kill it or harm its genes. If the genes are harmed but the cell still replicates, these genes can be passed on

Question 30

What is the most dangerous type of radiation in the body?

Answer 30

Alpha radiation, as its ionising power is much greater than that of the other two types

Question 31

What safety measures of workers take when handling radiation?

Answer 31

Keeping as far away as possible from the source, spending as little time as possible in risky areas, and shielding themselves by using thick concrete barriers and/or thick lead plates

Question 32

When is radiation used?

Answer 32

In automatic thickness machines, where beta particles are used to make sure the sickness of the aluminium is correct, and in smoke alarms to ionise the air between parts of the circuit so that is the current across that part drops - due to smoke absorbing the ions - and the alarm sounds

Question 33

What is activity in relation to radioactivity and what is its measurement?

Answer 33

Activity is the amount of unstable atoms in the source that decay per second. Its symbol is the Becquerel (Bq), which is 1 decay per second. As the atoms decay, they become stable, and so the activity decreases

Question 34

What is the half life of a group of radioactive atoms?

Answer 34

The time it takes for half of the atoms to decay - and so the activity to half

Question 35

Give 2 ways nuclear radiation is used in medicine

Answer 35

To detect whether a kidney is blocked - they give them a radioactive substance and detect the signals. If the signals go up and then stay there, then the kidney is blocked. To implant to get rid of cancerous tumours. This works as the radiation kills the tumour and then the substance should decay. Gamma rays in a narrow beam can be used to kill cancerous tumours. Gamma cameras can be used to see where a substance is absorbed into in the body. The patient is injected with a radioactive isotope and the camera senses where the radiation is coming from inside the body and uses that data to build up a picture

Question 36

How would you go about choosing an isotope to treat a patient?

Answer 36

Decide what type of treatment they need and then match the type of radiation they need with the type of isotope you supply. Then make sure the half life of the radioactive substance is short or long enough to decay before it in itself becomes a problem

Question 37

What is nuclear fission?

Answer 37

The splitting of an atom's nucleus into 2 smaller nuclei, releasing 2 or 3 neutrons and energy

Question 38

What can one fission cause?

Answer 38

A chain reaction, as each neutron released from the broken nucleus can cause other nuclei to break

Question 39

What is used to stop chain reactions in nuclear reactors?

Answer 39

Control rods to absorb the neutrons that come from the fissioned nuclei and adding unfashionable substances such as Uranium-238.

Question 40

Name 1 fissionable substance.

Answer 40

Uranium-235 and Plutonium-239

Question 41

How is fission caused in nuclear reactors?

Answer 41

They fire a neutron at high speed at the nucleus of the uranium or plutonium

Question 42

What is nuclear fusion?

Answer 42

The forcing together of 2 nuclei that have a relative mass of no more than 55 to form a larger nuclei

Question 43

Where is nuclear fusion taking place constantly?

Answer 43

In the centre of the sun and other stars

Question 44

Name 1 positive and 1 negative of nuclear fusion?

Answer 44

It is renewable, it could provide millions with energy, its fuel is easy found. It would also need a lot of energy to activate and the nuclei to be fused would be hard to control

Question 45

How does nuclear fusion in a reactor work?

Answer 45

The two nuclei are fired at each other at extremely high speeds. They need to bound together by the strong nuclear force, but have to be fired with enough kinetic energy to overcome the opposing forces of electrostatic repulsion (positive and a positive)

Question 46

What is radon gas and where does it come from?

Answer 46

A gas that emits alpha particles and seeps from the ground in some areas

Question 47

What changes might be instigated into future nuclear reactors?

Answer 47

Standard design that reduces build time and costs, a longer operating life, more safety features and less effect on the environment