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Explore Nuclear Decay

Worksheet Overview

QUESTION 1 of 10

In 2011, an earthquake hit Japan registering as a 9 on the Richter scale – the largest earthquake in Japan's history and the fourth biggest in the world. This created a tsunami six metres 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 from working correctly and three of them suffered meltdowns, spewing radioactive material into the environment. People were evacuated from their homes and a five km exclusion zone was set up to protect people from the danger 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 around us all the time. There are many sources of background radiation and this pie chart shows some of them:

 

 

A pie chart showing sources of background radiation.

 

When the nuclear commission was helping with 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 cause more or less damage depending on where they are. Let's 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 15 cm). It can be stopped by the skin and so it is safe if it remains outside 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 his 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 to, causing damage to them – but it can only do this twice.

 

a helium nucleus

 

 

Beta (β):

This is moderately ionising and can travel up to about one metre. It is not really safe inside or outside your body, so it’s best to stay away from it, full stop – but it is less likely to kill you than alpha, 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.

 

an electron

 

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.

 

gamma radiation

 

Neutrons (N):

These are the ones that you need to be afraid of and the ones that they were most concerned were being released from Fukushima. 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 it to release alpha, beta and gamma radiation.

 

a neutron

 

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

 

ionising radiation going through paper, aluminium and lead

 

So, now we need to look at how to write nuclear equations. Don’t worry – these are 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.

 

atomic number and mass number

 

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!

 

equation for thorium

 

 

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 equation 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? 

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 behave normally

They divide once and then stop

They divide out of control

Tick the pieces of equipment below that can be used to detect radioactivity.

Geiger Counter

Ratemeter

Burial Site

GM Tube

Background Cell

Loudspeaker

How many types of ionising radiation are there?

1

2

3

Tick the sources of background radiation shown in the list below.

Plants

Coal power stations

Cosmic rays

Air travel

Medical, e.g. X rays

Tick the main types of ionising radiation.

Alpha

Beta

Gamma

Delta

Epsilon

Zeta

Where does alpha, beta and gamma ionising 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

Lead

None

Which of the options below is radiation used for?

Cancer screening

Stabilisation of chemical substances

DNA mutations

  • Question 1

What does ionisation cause? 

CORRECT ANSWER
It changes the structure of an atom
It causes DNA to mutate
EDDIE SAYS
There were two correct answers to this first question - well done if you got them both! Ionisation changes the structure of an atom and so causes DNA mutations.
  • Question 2

What do cancerous cells do?

CORRECT ANSWER
They divide out of control
EDDIE SAYS
Even though this looked like a tricky question, once you look at the three options, it's not really that hard to eliminate the first two as being incorrect, is it? Cancerous cells divide so quickly that it is impossible to control them, causing the cancer to spread very quickly.
  • Question 3

Tick the pieces of equipment below that can be used to detect radioactivity.

CORRECT ANSWER
Geiger Counter
Ratemeter
GM Tube
Loudspeaker
EDDIE SAYS
This time there were four options to tick. How did you get on? Radioactivity can be measured using a Geiger-Müller (GM) tube connected to a ratemeter or counter. Most commonly, it is called a Geiger counter. Radioactivity can also be heard through a loudspeaker.
  • Question 4

How many types of ionising radiation are there?

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

Tick the sources of background radiation shown in the list below.

CORRECT ANSWER
Cosmic rays
Air travel
Medical, e.g. X rays
EDDIE SAYS
Halfway there already! Keep going, you're doing really well! Background radiation comes from a large number of sources but the ones listed above are cosmic rays, medical use (e.g. X rays) and also air travel. Other key sources include gamma rays from the ground, internal sources such as food, and nuclear waste.
  • Question 6

Tick the main types of ionising radiation.

CORRECT ANSWER
Alpha
Beta
Gamma
EDDIE SAYS
There were three options to tick here. The three main types of ionising radiation are alpha, beta and gamma.
  • Question 7

Where does alpha, beta and gamma ionising radiation come from?

CORRECT ANSWER
The nucleus of a radioactive atom
EDDIE SAYS
Oh, that was a tricky one, wasn't it? Did you go for the correct option? Alpha, beta and gamma ionising radiation comes from the nucleus of a radioactive atom.
  • Question 8

Is the following statement true or false?

 

Alpha rays are absorbed by a thin piece of paper.

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

What material can stop gamma rays?

CORRECT ANSWER
None
EDDIE SAYS
Nearly there - you've reached the penultimate question. Gamma rays radiate infinitely and can penetrate concrete and a thick block of lead - there's no stopping them! The good news though is that they normally pass straight through things without causing damage. Phew!
  • Question 10

Which of the options below is radiation used for?

CORRECT ANSWER
Cancer screening
EDDIE SAYS
Although radiation can sometimes cause types of cancer, it is also used in radiotherapy to screen for and treat the condition. Additionally, gamma radiation is used by doctors for sterilisation of medical instruments. Other uses of radiation include in fire alarms and to measure the thickness of materials in industry. Well done for completing this activity - this is a fairly challenging subject so you did well to get to the end! If you are unsure about some of the questions or answers, why not re-read the Introduction at the start of the activity and then have another go. Practice always helps understanding, as well as being an aid to memory.
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