Topic 7 - Radioactivity

Question 1

What did Ernest Rutherford learn about the properties of different types of radiation?

Answer 1

That alpha particles were stopped by paper and beta particles went through paper. Scientists later discovered gamma radiation which is even more penetrative than alpha or beta.

Question 2

What did Democritus believe about the atom?

Answer 2

That it was a hard, indivisible ball of metal that made up the universe.

Question 3

JJ Thompson discovered the electron and created the plum pudding model, what was this model like?

Answer 3

There was a sea of positive charge in the nucleus with scattered electrons of negative charge floating around in a random arrangement.

Question 4

What did Geiger and Marsden discover about the nucleus and how did they do this?

Answer 4

They fired alpha particles at gold foil in vacuum, more than 99% of particles went straight through but a small part of them reflected back, making them realise there was a dense concentration of positive charge in the nucleus and that most of the atom was empty space, Rutherford designed a new model because of this breakthrough.

Question 5

What was the problem with Rutherford’s model?

Answer 5

There was a missing sub-atomic particle which meant masses of elements were off.

Question 6

What did Niels Bohr add to Rutherford’s model?

Answer 6

He discovered that electrons orbited the nucleus in shells.

Question 7

What did James Chadwick do to change the atomic model?

Answer 7

He discovered neutrons from the mass discrepancies in nuclei and realised that they had no charge and thus no effect on the charge of the atom but it fixed the problem with the mass.

Question 8

The number of protons an element has is known as its?

Answer 8

Atomic number.

Question 9

The number of protons and neutrons in the nucleus is known as the?

Answer 9

Mass number.

Question 10

What is the relative charge and mass of a proton?

Answer 10

Relative mass of 1 and a relative charge of +1

Question 11

What is the relative charge and mass of a neutron?

Answer 11

Relative mass of 1 and a relative charge of 0.

Question 12

What is the relative charge and mass of an electron?

Answer 12

Relative mass of 1/2000 and a relative charge of -1.

Question 13

What an isotope?

Answer 13

An atom with a different number of neutrons from the normal amount in that element.

Question 14

What is activity?

Answer 14

The number of unstable atoms that decay per second in a radioactive source.

Question 15

What is alpha radiation?

Answer 15

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

Question 16

What is beta radiation?

Answer 16

Beta particles that are high energy electrons created in and emitted from unstable nuclei.

Question 17

What is a chain reaction?

Answer 17

Reactions in which one reaction causes further reactions which cause further reactions and etc.

Question 18

What is the count rate?

Answer 18

The number of decays recorded per second by a Geiger counter.

Question 19

What is gamma radiation?

Answer 19

Electromagnetic radiation emitted from unstable nuclei in radioactive substances.

Question 20

What is a radioactive material’s half-life?

Answer 20

The average time taken for the number of nuclei of the isotope to halve.

Question 21

What is ionisation?

Answer 21

Where atoms become charged.

Question 22

What does it mean if an object has been irradiated?

Answer 22

It has been exposed to ionising radiation.

Question 23

What is a moderator in a nuclear reactor?

Answer 23

A substance in a nuclear reactor that slows down fission neutrons.

Question 24

What is nuclear fission?

Answer 24

The process in which certain nuclei like Uranium-235 spilt into two fragments, releasing extremely large amounts of energy and two or three neutrons.

Question 25

What is a nuclear fission reactor?

Answer 25

Reactors that release energy steadily due to the fission of an isotope.

Question 26

What is nuclear fusion?

Answer 26

The process wherein small nuclei are forced together to fuse and form a larger nucleus, releasing large amounts of energy.

Question 27

What is radioactive contamination?

Answer 27

The unwanted presence of radioactive atoms on other materials.

Question 28

What is a reactor core?

Answer 28

The thick steel vessel used to contain fuel rods, control rods and the moderator in a nuclear fission reactor.

Question 29

What is radiation measured in?

Answer 29

Becquerels.

Question 30

What is background radiation?

Answer 30

Radiation in the natural world that is so small that it isn’t harmful.

Question 31

Complete this equation for the decay of Carbon-14.
C (14/6) -> N (14/7) + ______.

Answer 31

e(0/-1)

Question 32

Rank the three types of radiation in terms of ionising power (gamma/alpha/beta).

Answer 32

1. Alpha
2. Beta
3. Gamma

Question 33

Rank the three types of radiation in terms of penetration power (alpha/beta/gamma).

Answer 33

1. Gamma
2. Beta
3. Alpha

Question 34

Rank the three types of radiation in terms of range in air (alpha/beta/gamma).

Answer 34

1. Gamma (infinity)
2. Beta (1 metre)
3. Alpha (few cm)

Question 35

Rank the three types of radiation in terms of mass (gamma/beta/alpha).

Answer 35

1. Alpha (large mass)
2. Beta (very small mass)
3. Gamma (no mass)

Question 36

What types of radiation can penetrate the skin out of alpha, beta and gamma?

Answer 36

Only beta and gamma.

Question 37

1 Becquerel is equal to?

Answer 37

1 decay per second.

Question 38

The decay of an atom is not able to be predicted but what can we do?

Answer 38

We can estimate how many will decay per second.

Question 39

What is the equation for working out half-lives?

Answer 39

Amount of n half-lives = (1/2)n x initial amount.

Question 40

If 100g of Uranium-235 has a half-life of 4 hours, how much Uranium will decay after 24 hours?

Answer 40

100g x (1/2)6 = 25/16 or 1.5625 grams.

Question 41

What is radiotherapy?

Answer 41

The usage of radioactive chemicals to kill tumour cells.

Question 42

What do radioactive tracers do?

Answer 42

Radioactive tracers trace the flow of a substance through the body using normally beta or gamma radiation.

Question 43

What are daughter nuclei?

Answer 43

The products of emitting radiation.

Question 44

What is used to detect gamma radiation in a substance?

Answer 44

A gamma camera.

Question 45

What is a functional scan?

Answer 45

It is an operation that helps show us how well the body is functioning,

Question 46

What is the equation linking energy, mass and the speed of light?

Answer 46

Energy (J) = mass (kg) x speed of light (m/s) squared or E = mc2

Question 47

How is E = mc2 useful in radiation?

Answer 47

It shows how much energy is released when an amount of mass is destroyed. If 1 gram of an isotope was destroyed here, 9 x10 to the power of 13 joules of energy would be released! That looks like this 90000000000.

Question 48

What is deuterium?

Answer 48

An isotope of Hydrogen with an extra isotope, occurring on very rare occasions.

Question 49

What is tritium?

Answer 49

An isotope of Hydrogen that contains 2 extra protons and occurs extremely rarely.

Question 50

What uses nuclear fusion as its source of energy?

Answer 50

Every star in the universe.

Question 51

What do we use to detect background radiation?

Answer 51

A geiger counter.

Question 52

What two sources of natural background radiation are there?

Answer 52

Certain radioactive rocks like granite.

Cosmic rays, very high energy particles that travel through a vacuum to the Earth’s atmosphere.

Question 53

What two manmade sources of background radiation are there?

Answer 53

Nuclear weapons testing that has released radioactive isotopes into the environment.

Accidents at nuclear power stations like the Chernobyl disaster.

Question 54

What is radiation dose measured in?

Answer 54

Sieverts.