Radioactivity
Radioactive materials have unstable nuclei which try to
“decay”into more stable nuclei. They do this by emitting
particles from their nucleus.
There are two types of particle, Alpha and Beta.
Alpha Decay α
Some elements decay by emitting alpha particles. These
consist of 2 protons and 2 neutrons (the same as a helium
nucleus). Radium decays to Radon by alpha emission.
“decay”into more stable nuclei. They do this by emitting
particles from their nucleus.
There are two types of particle, Alpha and Beta.
Alpha Decay α
Some elements decay by emitting alpha particles. These
consist of 2 protons and 2 neutrons (the same as a helium
nucleus). Radium decays to Radon by alpha emission.
226
222
86
Rn
4
2
(note. the top number is the atomic mass (protons + neutrons) and
the bottom number is the atomic number ( number of protons))
Beta Decay β
14
6
14
7
N
0
-1
Gamma emission γ
After alpha or beta particles have been emitted the
nucleus can remain in an “exited state. The protons
and neutrons are rearranged resulting in γ emission.
Gamma emission is not in the form of particles, it is
high energy electomagnetic radiation.
nucleus can remain in an “exited state. The protons
and neutrons are rearranged resulting in γ emission.
Gamma emission is not in the form of particles, it is
high energy electomagnetic radiation.
Penetration by alpha,beta particles
and Gamma rays
Alpha particles are the least penetrating and are
easily stopped by a sheet of paper and only
travel a few cm in air
Beta particles can pass through paper but can be
stopped by a thin sheet of aluminium and can
travel several metres in air
Gamma rays are very penetrating and are only stopped
by many cm of lead.
and Gamma rays
Alpha particles are the least penetrating and are
easily stopped by a sheet of paper and only
travel a few cm in air
Beta particles can pass through paper but can be
stopped by a thin sheet of aluminium and can
travel several metres in air
Gamma rays are very penetrating and are only stopped
by many cm of lead.