Download `background radiation`.

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
PARTICLE
Proton
Neutron
Electron
RELATIVE
MASS
1
1
0
CHARGE
+
0
-
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.
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
Unstable nucleus
New nucleus
Alpha
particle
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.
The Atomic number
decreases by a value
of 1.
What do
you notice?
BETA
Unstable
nucleus
New
nucleus
Beta
particle
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.
The atomic structure
doesn’t fundamentally
change.
What do you
notice?
GAMMA
Unstable
nucleus
New
nucleus
Gamma
radiation
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.
Types of radiation
Unstable
nucleus
New
nucleus
Alpha
particle
Beta
particle
Unstable
nucleus
New
nucleus
Unstable
nucleus
New
nucleus
Gamma
radiation
Alpha () – a high speed
helium nucleus is emitted
(2 protons & 2 neutrons).
Beta () – the fast moving,
high energy electron is
called a beta particle.
Gamma (g) – after  or 
decay surplus energy is
sometimes emitted.
Gamma radiation is a wave
with very high frequency
with short wavelength.
Type of
radiation
Symbol
What is
it made
from?
Alpha

Helium
nucleus. 2
protons &
2 neutrons
Beta

High speed
electron
Gamma
g
High
energy
wave
How far
will it
travel in
air?
What
stops
it?
PROPERTIES
Alpha, Beta and Gamma all have
different properties:
• They travel different distances
• Different strengths
• 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.


g
Alpha, Beta, Gamma, Thick lead, Paper,
Aluminium
Type of
radiation
Symbol
What is
it made
from?
How far
will it
travel in
air?
cm
What
stops
it?
Alpha

Helium
nucleus. 2
protons &
2 neutrons
Beta

High speed m
electron
Aluminium
Gamma
g
High
energy
wave
Thick lead
&
concrete
Lots of m
Air /paper
Quiz
1.What do you call the centre of
an atom?
A) Electron
B) Nucleus
C) Proton
D) Neutron
Quiz
2.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
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.
IONIZING RADIATION
What does this mean?
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.
Ionisation
When 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
Radiation is always present in the
environment. We call this ‘background
radiation’. There are many sources of
background radiation, these include:
Natural
Man-made
Cosmic rays, Food,
Rocks (particularly
granite) & Radon
gas.
Hospitals, Nuclear
bombs and
testing, Nuclear
power stations &
accidents
13% are
man-made
Background Radiation
Radon gas
Food
Cosmic rays
Gamma rays
Medical
Nuclear power
Isotopes
An isotope is an atom with a different number of neutrons:
Notice that the mass number is different. How many
neutrons does each isotope have?
Each isotope has 8 protons – if it didn’t then it just
wouldn’t be oxygen any more.
A “radioisotope” is simply an isotope that is radioactive
– e.g. carbon 14, which is used in carbon dating.
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.
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?
Exam questions