Unit 2: 6 - Radioacitivty

Question 0

How does a radioactive substance become stable?

Answer 0

By emitting radiation, making the nuclei stable.

Question 1

What is a radioactive substance?

Answer 1

A substance which contains unstable nuclei.

Question 2

How do we predict or influence the radioactive decay of a substance?

Answer 2

We can’t. It is completely random.

Question 3

What is background radiation?

Answer 3

The radiation that we naturally come into contact with in our daily lives. It can be from rock, space (cosmic radiation), power stations, food, and a lot more.

Question 4

How does radon enter the body?

Answer 4

Through the lungs, as it is a gas.

Question 5

What is an atom made up of?

Answer 5

A nucleus composed of protons and neutrons, orbited by electrons. There is a lot of empty space.

Question 6

What is the natural process of a radioactive substance becoming stable?

Answer 6

Radioactive decay

Question 7

What was the name of the experiment used to discover the positive charge of the nucleus? Who did it? What did it consist of? What were the results?

Answer 7

Alpha particle scattering. By Rutherford, Geiger and Marsden. Alpha particles were fired at thin gold foil. Most particles went straight through, showing that the atom was mostly empty space. Some rebounded through very large angles, suggesting the nucleus has a large mass and a very large positive charge. (Some deflected through small angles, showing that the nucleus had a positive charge)

Question 8

What change is there in the nucleus from alpha decay?

Answer 8

The nucleus loses 2 protons and 2 neutrons

Question 9

What change is there is there in the nucleus from beta decay?

Answer 9

A neutron in the nucleus changes into a proton and an electron.
neutron (0) -> proton (+1) + electron (-1)

Question 10

What is emitted from alpha decay?

Answer 10

2 protons and 2 neutrons as an alpha particle (a positive helium ion with no electrons)

Question 11

What is emitted in a beta particle?

Answer 11

An electron

Question 12

What is the relative masses and charge of each part of an atom?

Answer 12

Proton 1 +1
Neutron 1 0
Electron 0.0005 (1/2000th) -1

Question 13

A charged atom is called an ____

Answer 13

Ion

Question 14

Atoms with different numbers of neutrons are ____

Answer 14

Isotopes

Question 15

What is the relative charge of an alpha particle?

Answer 15

+2 as it has 2 protons and no electrons.

Question 16

What is the relative charge of a beta particle?

Answer 16

-1 as it is just one electron.

Question 17

What does carbon-14 become when it emits a beta particle? Explain.

Answer 17

It loses one neutron and becomes an electron and a proton. The mass number stays the same, but it becomes nitrogen.

Question 18

What deflects alpha and why?

Answer 18

Magnetic and electric fields as they have a positive charge.

Question 19

What is the order of least->most ionising?

Answer 19

Gamma>Beta>Alpha

Question 20

What is order of penetration from least->most?

Answer 20

Alpha (stopped with paper) > Beta (Stopped with an aluminium sheet) > Gamma (Stopped with lead or lots of concrete)

Question 21

What are the problems in life forms with ionising?

Answer 21

Particles knock electrons off atoms which can join onto others, damaging the molecule. DNA can be mutated which will reproduce, and makes cancerous tumours.

Question 22

Why are alpha particles least penetrating?

Answer 22

They are large so they have lots of collisions.

Question 23

Why are beta particles more ionising?

Answer 23

They are smaller and and move a lot faster.

Question 24

Why is gamma most penetrating?

Answer 24

As it is an electromagnetic wave, it can travel a long way and very quickly before collision.

Question 25

How do we measure radioactivity?

Answer 25

We measure the count rate

Question 26

What is half-life?

Answer 26

Half life is the measure of how quickly the radioactivity count decreases to half of its original value. Or we can define it as the time it takes for the unstable nuclei to halve.

Question 27

What source is used in smoke alarms?

Answer 27

An alpha source, americium-238

Question 28

What source would be used for thickness monitoring in metal foil?

Answer 28

Beta

Question 29

What sources would be used as tracers in medicine? And why?

Answer 29

Beta and gamma. They are most penetrating and least ionising.

Question 30

What is radioactive dating?

Answer 30

It is a technique used to find the age of ancient material. Uranium dating is used in igneous rocks and carbon dating is used in wood and other organic material.