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Nucleon Number A
Proton Number Z
Certain nuclei are unstable. They decay
spontaneously and emit a particle (either
alpha or beta) and nucleus forms an isotope
of a new element.
Unstable = Radioactive
Decay = Disintegrate
Random = Spontaneous
Low level radiation in our environment.
Mostly naturally occuring.
The sun as cosmic rays, radioactive rocks,
Nuclear radiation can knock electrons out of
atoms in the air or in your body. This leaves
the atom positively charged as an ion.
Alpha particles are made of 2 protons and 2
This means that they have a charge of +2,
and a mass of 4.
Alpha particles are relatively slow and
They have a low penetrating power - you
can stop them with just a sheet of paper.
Because they have a large charge, alpha
particles ionize other atoms strongly
•Beta particles have a charge of
minus 1, and a mass of about
1/2000th of a proton. .
•They are fast, and light.
•Beta particles have a medium
penetrating power - they are
stopped by a sheet of aluminum
•Beta particles ionize atoms that
they pass, but not as strongly as
alpha particles do.
•Gamma rays are waves, not particles.
This means that they have no mass and no
•Gamma rays have a high penetrating power
- it takes a thick sheet of metal such as lead,
or concrete to reduce them significantly.
•Gamma rays do not directly ionize other
•We don't find pure gamma sources - gamma
rays are emitted alongside alpha or beta
particles. Strictly speaking, gamma emission
isn't 'radioactive decay' because it doesn't
change the state of the nucleus, it just carries
away some energy.
Atoms are unstable and they break up or
decay to form stable nuclei.
The decay is random
The decay causes new elements to be formed.
The decay process is different for alpha, beta,
and gamma emissions.
A substance loses 2 protons and 2
neutrons when alpha particle is given off.
• mass number stays the same
• proton number increases by one
• electron leaves the nucleus at high speed.
This is the amount of time taken for half the
nuclei of a radioactive substance to decay.
4. Thickness monitoring
5. Carbon Dating- after an organism dies the
amount of C-14 inside it begins to decay. It can
be used to find out how old a substance is.
6. Dating Rocks
By ionising atoms, radiation causes chemical
reactions to occur in living cells. The damages
the cell’s DNA and leads to mutation.
Mutation causes cancer.
SIX MAIN PRECAUTIONS:
1. Use sealed containers
2. Use tongs
3. Display the warning sign
4. Wear radiation badge
5. Minimize exposure
6. No eating or drinking