# Nuclear Decay

In this worksheet, students explore the different types of radiation and how they are formed.

Key stage:  KS 4

Curriculum topic:  Physics: Atomic Structure

Curriculum subtopic:  Ionisation

Difficulty level:

### QUESTION 1 of 10

In 2011, an earthquake hit Japan registering as a 9 on the Richter scale – the largest earthquake in Japans history and the 4th biggest in the world. This created a tsunami 6 meters high and killed over 15,000 people. One of the places hit by the earthquake was a town called Fukushima where they had a nuclear reactor. Unfortunately – the damage caused by the tsunami stopped the reactors form working correctly and three of the reactors suffered meltdowns spewing radioactive material into the environment. People were evacuated from their homes and a 5km exclusion zone was set up to protect people from the damage of the radiation. But what is radiation and how is it caused? This is what we will be looking at in this activity.

There is a level of background radiation is all around us all the time. There are many sources of background radiation. The pie chart shows some of them:

When the nuclear commission was helping the clean-up from Fukushima, they took a range of readings looking for different types of radiation. They needed to do this because different types of radiation each cause more or less damage depending on where they are. Lets look at the different types of radiation in detail:

Alpha (α):

Alpha radiation causes the most ionisation, but only travels a very short distance before it stops (about 15cm). it can be stopped by the skin and so it is safe outside of your body – but if you inhale it or drink it, then it can be deadly. A Russian spy, Litvinenko, was killed by a VERY small amount of alpha radiation being put in their tea.

Alpha radiation is made of 2 Protons and 2 Neutrons – it is a helium nucleus. This gives it a charge of +2, meaning that it will rip electrons off things it comes near causing damage to them – but it can only do this twice.

Beta (β):

This is moderately ionising and can travel up to about 1 meter. It is not really safe inside or outside your body, so it’s best to stay away from it full stop – but unlike alpha, it is less likely to kill you unless you have a high dosage of it.

It is made of a fast-moving electron usually spat out from the inside of a nucleus. It causes damage by hitting other electrons and removing them from their atoms.

Gamma (γ):

This is a strange one because it is a wave, not really a particle (although it is carried by photons). It is the least ionising of all of the three that we have looked at so far because it needs to hit stuff at just the right speed to cause damage. So as a result, it normally just passes through everything. Safe on the inside and the outside, unless there is a lot of it.

Neutrons (N):

These are the ones that you need to be afraid of and the ones that they were most concerned where being realised from Fukuhara. They are made of a Neutron (who would have guessed, right?) and they are so dangerous because if they collide with a nucleus then they will make the nucleus itself radioactive, causing ti to release alpha, beta and gamma radiation.

Alpha, beta, gamma and neutron radiation come from the nucleus of a radioactive atom. and gamma causes the least. Alpha can be stopped by a thin piece of paper, beta penetrates the paper but can be stopped by a 3mm thick piece of aluminium and gamma can penetrate a 3m thick lead block and concrete. The diagram shows this in more detail:

So – now we need to look at how to write nuclear equations. Don’t worry – this is the easiest equations you will ever do!

The first thing you need to know is what the Atomic number and Mass number are. Mass number is the number of Neutrons and Protons in the nucleus and Atomic number is the number of protons only.

So – when we have an alpha decay, the original atom needs to lose 2 protons and 2 neutrons – this means that it will take 4 from the mass number and 2 from the atomic number. This, in turn, makes a new atom – thorium in this case – with a mass number of 4 less and an atomic number of 2 less.

Key point – the number needs to be the same on each side!

When doing Beta decay, a neutron turns into a proton. This will not change the mass number, but it will change the atomic number. A beta particle is an electron, so has a mass number of 0. It also has an atomic number of -1 because it has the opposite charge of a proton. This nuclear question looks like this:

Key point – the number needs to be the same on each side!

And that's it - now questions!

What does ionisation cause? Tick two options.

it changes the structure of an atom

it stabilises atoms

it hardens crude oil

it causes DNA to mutate

What do cancerous cells do?

they are normal

they divide and then stop

they divide out of control

Tick four pieces of equipment that can be used to detect radioactvity.

Geiger counter

ratemeter

burial site

GM tube

background cell

loudspeaker

How many types of ionising radiation are there?

1

2

3

Tick three sources of background radiation.

plants

coal power stations

cosmic rays

air travel

medical, e.g. X rays

Tick the three main types of ionising radiation.

alpha

beta

gamma

delta

epsilon

zeta

Where do these types of radiation come from?

the nucleus of a radioactive cell

the nucleus of a radioactive atom

cancerous cells

Is the following statement true or false?

Alpha rays are absorbed by a thin piece of paper.

true

false

What material can stop gamma rays?

aluminium

none

cancer screening

stabilisation of chemical substances

DNA mutations

• Question 1

What does ionisation cause? Tick two options.

it changes the structure of an atom
it causes DNA to mutate
EDDIE SAYS
Ionisation changes the structure of an atom and causes DNA mutations.
• Question 2

What do cancerous cells do?

they divide out of control
EDDIE SAYS
Cancerous cells divide so quickly that it is impossible to control them, causing the cancer to spread very quickly.
• Question 3

Tick four pieces of equipment that can be used to detect radioactvity.

Geiger counter
ratemeter
GM tube
loudspeaker
EDDIE SAYS
Radioactivity can be measured using a Geiger-Müller (GM) tube connected to a ratemeter or counter. Most commonly it is called Geiger counter. Radioactivity can also be heard through a loudspeaker.
• Question 4

How many types of ionising radiation are there?

3
EDDIE SAYS
There are three main types of ionising radiation: alpha (α), beta (β), gamma (γ).
• Question 5

Tick three sources of background radiation.

cosmic rays
air travel
medical, e.g. X rays
EDDIE SAYS
Background radiation comes from cosmic rays, medical use (e.g. X rays), gamma radiation from the ground, internal (e.g. food), air travel, nuclear waste etc.
• Question 6

Tick the three main types of ionising radiation.

alpha
beta
gamma
EDDIE SAYS
The three main types of ionising radiation are alpha, beta and gamma.
• Question 7

Where do these types of radiation come from?

the nucleus of a radioactive atom
EDDIE SAYS
Alpha, beta and gamma ionising radiation comes from the nucleus of a radioactive cell.
• Question 8

Is the following statement true or false?

Alpha rays are absorbed by a thin piece of paper.

true
EDDIE SAYS
Alpha rays are absorbed by a thin piece of paper, beta penetrates the paper but can be stopped (absorbed) by a 3mm thick piece of aluminium and gamma can penetrate a 3m thick lead block and concrete.
• Question 9

What material can stop gamma rays?

none
EDDIE SAYS
Gamma rays radiate infinitely and can penetrate concrete and a thick block of lead.
• Question 10

cancer screening
EDDIE SAYS
It is used in radiotherapy to treat cancer. Gamma radiation, specifically, is used by doctors for sterilisation of medical instruments. Additionally, it is used for screening for cancer, fire alarms and to measure thickness in the industries.
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