Radioactivity

Learning objectives:To be able to recall and explain the structure and properties of the atom.

To be able to recall the three main types of radiation.

To be able to explain the structure and properties of the three main forms of radiation.

Everything is made up of miniscule particles called ATOMS. Inside atoms are even smaller particles.

Can you name the parts of the atom?ELECTRONS orbit the nucleus

This is the NUCLEUS.

PROTONS and NEUTRONS are found in the nucleus

There are usually equal numbers of Protons and Electrons in the atom. WHY?

This is because they carry opposite charges. If you have an equal number of + and – charges they will cancel each other out so we get a balanced or neutral atom.

PARTICLE RELATIVE MASS

CHARGEPARTICLE RELATIVE MASS

CHARGE

Proton 1 +Neutron 1 0Electron 0 -

Is this a stable (balanced) atom?

Why?

What is the MASS NUMBER?5 (three Protons & two Neutrons)

MASS NUMBER = number of protons + number of

neutrons

SYMBOL

ATOMIC NUMBER = number of protons

RADIOACTIVE MATERIALS

Most atoms are stable. However, radioactive atoms are not – they are unbalanced and unstable.

They ‘want’ to become stable (balanced). So to try to achieve this state they emit (give out) energy in the form of radiation.

This releases ENERGY. Sometimes a MASSIVE amount of energy. Can you think of any examples?

We’ll look at examples and uses in more detail in another lesson.

TYPES OF RADIATION

How many types of radiation are there and how are they different?

What are they?

What do you notice?

So, what is an alpha particle?

ALPHA

Alpha () – an atom decays into a new atom and emits an alpha particle (2 protons and 2 neutrons)

Alpha radiation is the nucleus of a helium atom travelling at extremely high speed.

Unstable nucleus

New nucleus

Alpha particle

What do you notice?

The Atomic number decreases by a value of 1.

Beta () – an atom decays into a new atom by changing a neutron into a proton and electron. The fast moving, high energy electron is called a beta particle.

Unstable nucleus

New nucleu

s

Beta particle

BETA

What do you notice?

The atomic structure doesn’t fundamentally change.

GAMMA

Gamma – after or decay surplus energy is sometimes emitted. The atom itself is not changed. Gamma radiation is part of the EM Spectrum; a wave with a very high frequency, very short wavelength.

Unstable

nucleus

New nucleu

s

Gamma radiatio

n

Type of radiatio

n

Symbol

What is it made from?

How far will it travel

in air?

What stops it?

                     

Types of radiationAlpha () – a high speed helium nucleus is emitted (2 protons & 2 neutrons).Beta () – the fast moving, high energy electron is called a beta particle.Gamma () – after or decay surplus energy is sometimes emitted. Gamma radiation is a wave with very high frequency with short wavelength.

Unstable nucleus

Unstable nucleus

Unstable nucleus

New nucleus

New nucleus

New nucleus

Alpha particle

Beta particle

Gamma radiation

Type of radiation

SymbolWhat is it made from?

How far will it travel in air?

What stops it?

Alpha   Helium nucleus.

2 protons

& 2

neutrons

   

Beta   High speed

electron

   

Gamma High energy wave

   

PROPERTIESAlpha, Beta and Gamma all have different properties:

• Different strengths

• They travel different distances

• They are stopped by different

materials.DEMO…

Radioactivity

Copy the diagram below and complete the arrows for each type. Then use the words at the bottom to construct an explanation in your own words.

Alpha, Beta, Gamma, Thick lead, Paper, Aluminium

Type of radiation

SymbolWhat is it made from?

How far will it travel in air?

What stops it?

Alpha   Helium nucleus.

2 protons

& 2

neutrons

   

Beta   High speed

electron

   

Gamma High energy wave

   

Type of radiation

SymbolWhat is it made from?

How far will it travel in air?

What stops it?

Alpha   Helium nucleus.

2 protons

& 2

neutrons

 cm Air /paper

Beta   High speed

electron

m  Aluminium

Gamma High energy wave

Lots of m 

Thick lead

& concrete

Quiz

1.What do you call the centre of an atom?

A) Electron

B) Nucleus

C) Proton

D) Neutron

Quiz2.A stable atom has…

A) Equal numbers of Protons & Electrons

B) Different numbers of Protons

C) Equal numbers of Electrons & Neutrons

D) Equal numbers of Protons & Electrons

Quiz

3.How many types of radiation are there?

A) 3

B) 9

C) 2

D) 4

Quiz

4.Radiation is emitted from…

A) All atoms

B) Most atoms

C) Unstable atoms

D) Stable atoms

Quiz

5.An alpha particle consists of…

A) 2 protons

B) A high speed electron

C) A wave

D) 2 protons and 2 neutrons

Quiz

6.Beta radiation is…

A) 2 protons

B) A high speed electron

C) A wave

D) 2 protons and 2 neutrons

Quiz

7.Gamma radiation is…

A) 2 protons

B) A high speed electron

C) A wave

D) 2 protons and 2 neutrons

Quiz

8.Alpha is stopped by…

A) Thick lead

B) Thin paper

C) A few cm of air

D) Aluminium

Quiz

9.Beta is stopped by…

A) Aluminium

B) Paper

C) Lead

D) Concrete

Quiz

10. Gamma is mostly stopped by…

A) A few cm of air

B) Thick lead

C) Aluminium

D) Paper

HAVE WE MET THE LEARNING OBJECTIVES?

Can you recall and explain the structure and properties of the atom?Do you know the three main types of radiation?

Are you able to explain the structure and properties of the three main forms of radiation?

The End

Well Done!

Learning objectives:To be able to recall and explain the structure and properties of the 3 forms of radiation.To be able to explain the ionising properties of the 3 forms of radiation.

To be able to understand and explain the term ‘background radiation’ with examples.

ACTIVITY – individual task:

Complete the 12 questions about Alpha and Beta decay (on the sheet).

Then stick it into your book.

ALPHA & BETA decay answers…Alpha decay

(i) 92, (ii) 222, (iii) 204 (top) and 82 (bottom), (iv) He.

Beta decay

(i) 91, (ii) 131, (iii) 6 (top) and 3 (bottom), (iv) 24 (top) and 11 (bottom).Alpha or Beta?

(i) Beta, (ii) Alpha, (iii) Alpha, (iv) Beta.

When a charged particle comes near another atom, it can pull electrons off the atom.

This slows the particle down. The atom is then called an ion. If it has lost electrons, it is a positive ion.

IONIZING RADIATION What does this mean?

IonisationWhen radiation collides with neutral atoms or molecules it alters their structure by knocking off electrons. This will leave behind IONS – this is called IONISING RADIATION.

particle

Electron

So, what forms of radiation can be ionizing?Only a charged particle such as an or a can be ionizing.

What about Gamma?Gamma has no ionizing power. But it is still the most powerful radiation but passes through most objects.

BACKGROUND RADIATION

Where does radiation come from and what are the sources of radiation?

ACTIVITY – In pairs/threes:

In your book, make a list of as many possible sources of radiation you can think of.

Make sure you consider natural and man-made sources.

A Neutron walks into a bar and asks the bartender ‘How much for a beer?’

The bar tender says…

‘For you sir, no charge’

BACKGROUND RADIATION

Radiation is always present in the environment. We call this ‘background radiation’. There are many sources of background radiation, these include:Natural

Cosmic rays, Food, Rocks (particularly granite) & Radon gas.

Man-made

Hospitals, Nuclear bombs and testing, Nuclear power stations & accidents

Have the LO been met?

To be able to recall and explain the structure and properties of the 3 forms of radiation.To be able to explain the ionising properties of the 3 forms of radiation.

To be able to understand and explain the term ‘background radiation’ with examples.

ACTIVITY – individual task:

Complete the pie chart on the worksheet to represent the data about background sources of radiation.

Stick it into your book.

Background Radiation

Radon gas

Food

Cosmic rays

Gamma rays

Medical

Nuclear power

13% are man-made

Learning objectives:To be able to recall and explain the different forms of background radiation.

To be able to explain the meaning of the term ‘isotope’.

To be able to understand and explain the how ionising radiation can be damaging to living cells.

IsotopesAn isotope is an atom with a different number of neutrons:

Each isotope has 8 protons – if it didn’t then it just wouldn’t be oxygen any more.

Notice that the mass number is different. How many neutrons does each isotope have?

A “radioisotope” is simply an isotope that is radioactive – e.g. carbon 14, which is used in carbon dating.

ACTIVITY – group task in pairs/threes:

Read the information sheet about the poisoning of the ex spy.

Create a poster to explain how the ex-spy Alexander Litvinenko was killed AND why Polonium-210 is so dangerous if ingested.

Have the LO been met?

To be able to recall and explain the different forms of background radiation.

To be able to explain the meaning of the term ‘isotope’.

To be able to understand and explain the how ionising radiation can be damaging to living cells.

The End

Well Done!

An atom bumps into a friend in the street and says ‘I’ve lost an electron’

The friend says ‘Are you sure’. The Atom says…‘Yes, I’m positive’

Quick Quiz!

1.What does the term ionization mean?

2.What types of radiation cause ionization?

3.What is an isotope?

4.What is a radioisotope?

Quick Quiz!

1.What does the term ionization mean? When charged particles are produced – either gaining or removing electrons from particles.

2.What types of radiation cause ionization? Only Alpha and Beta.

3.What is an isotope? Atoms of the same element with a different Mass number (i.e. different numbers of neutrons).

4.What is a radioisotope? An isotope/s of an element which emits nuclear radiation

Learning objectives:To appreciate that radiation can be harmful or beneficial.

To be able to explain how radiation can be used.

To be able to give examples of some of the common uses.

USES OF RADIATION

When we think of radiation, we think DANGER! Radiation is dangerous because it damages the DNA of living cells.

However, there are many ways which we can use radiation to our benefit.

ACTIVITY – Individual task:

You are going to find out about the different ways we use radiation.

Read each of the uses described on the information sheet. In your own words, write down the key information and match it up with one of the diagrams

Stick the picture in your book next to your description.

1.How does radiation kill cancer cells?

2.What is the benefit of using radiation as opposed to an operation to remove a tumour?

3.Why does smoke inside the detector trigger the alarm?

4.Which type of radiation would be used to measure the thickness of a) Paper, b) Aluminium foil and C) Sheet steel?

5.Why sterilize plastic medical equipment with radiation?

6.How could a tracer be used to find a blockage in a kidney?

Have the LO been met?

To appreciate that radiation can be harmful or beneficial.

To be able to explain how radiation can be used.

To be able to give examples of some of the common uses.

The End

Well Done!