1. By the end of this presentation you should be able to……
RADIOACTIVITY: TYPES OF RADIATION
By the end of this presentation you should be able to……
List the three types of nuclear radiation
Describe the nature of each type.
Complete equations that illustrate the different types of emission.

2. There are three types of radiation.
What is Alpha radiation? (a)
A clump of two protons and two neutrons,
A helium nucleus
4He 2
Is positively charged
It is the largest of all the three types of radiation.

3. 226Ra 222Rn + 4He 88 86 2 When it “throws out” a particle of
radiation, it is said to have “decayed”. Since the nucleus of this atom is now
different from the original, 86 protons
and 136 neutrons, this means a
new element
has been
formed, radon.
226Ra Rn He
This is an unstable atom of radium. It has 88 protons and ( ) 138 neutrons.
The alpha particle that is thrown out has alot of energy and can damage human cells.

4. 2. What is Beta radiation? (b)
A fast moving (high energy) electron.
It is negatively charged.
When a neutron in the nucleus disintegrates, it forms an electron (which is emitted as a beta particle) and a proton which remains in the nucleus.

5. Caesium-55 decays by beta emission and changes into barium-56.
This is what happens inside the nucleus.
137Cs Ba e

6. 3. What is Gamma radiation? (g)
High frequency electromagnetic radiation
No charge

7. Barium-137 is unstable and decays by gamma emission
Barium-137 is unstable and decays by gamma emission. The gamma ray takes some of the energy of the nucleus away with it so the remaining barium atom is more stable. The mass does not change.
Gamma ray
This type of radiation is usually emitted along with alpha or beta particles. It is the most penetrating of all three. For this reason it can be the most dangerous if the source of radiation is outside of the body.

8. UNDERSTANDING RADIOACTIVITY EQUATIONS
Almost every year, equations representing radioactive decay will appear within examination questions! You must try to remember the composition of particles of radiation, along with how they are represented in equations.
PARTICLE
MASS NUMBER
PROTON NUMBER
SYMBOL
Alpha 4 2
4He ; 4a
Beta -1
0e ; 0b
Remember that gamma radiation (g) may occur at the same time as the others and since it is an electromagnetic wave, will not affect the mass of the element.

9. Look carefully at how the mass numbers (at the top) add up to the same number before and after
226Ra Rn He
....a radiation
The proton numbers (at the bottom) should also add up to the same number before and after decay
137Cs Ba e
....b radiation
Examination questions may provide you with equations with some numbers missing and ask you to complete it, or to recognise the type of radioactivity being emitted.