1. The nucleus of an atom contains two particles:
RADIOACTIVITY
The nucleus of an atom contains two particles:
protons 
 neutrons

2. CHARGES The proton - has a positive charge The neutron - has no charge
The force between the protons is
repulsion
The force between the neutrons
or a neutron and a proton is
zero

3. WHAT HAPPENS?
The force between the protons is repulsive; the force between the neutrons is zero.
The particles in the nucleus should fly apart !!
Why doesn’t the nucleus fly apart?
There is another force within the nucleus called the
strong nuclear force that holds the nucleus together.

4. STRONG NUCLEAR FORCE
The strong nuclear force is much stronger than an electrostatic force, but it only works over extremely short distances.
As a result, sometimes the strong nuclear
force can’t hold the nucleus together - it
becomes unstable and undergoes
radioactive decay.

6. RADIOACTIVE DECAY Types of decay
When an atom changes from one element to another by emitting particles or decaying, its called a transmutation.
Types of decay
When a nucleus emits a particle with
two protons and two neutrons
(a helium nucleus)
weakest
Alpha decay ()
Beta decay ()
When a nucleus emits a high speed electron
Gamma decay ()
When a nucleus emits a high energy
photon
strongest