Some atoms are unstable and the nucleus (the centre of the atom) can break apart which can cause some energy, or even a small particle to burst out. This is called nuclear radiation.

There are three main types of radiation:

• alpha particles: These are small bits of nucleus. They are made of 2 protons and 2 neutrons. They have a positive electric charge.
• beta particles: These are the loose electrons left over when the atoms breaks apart. They have a negative electric charge.
• gamma rays: These are actually electromagnetic energy waves. They do not have an electric charge.

Of the three types of radiation, alpha particles are the ones that can cause the most damage to living things. However, alpha particles can be stopped by our skin, or even a thick sheet of paper. They are not very penetrating.

Beta particles can pass through paper (and our skin) but they are not as damaging as the alpha particles. A thick piece of aluminium will stop beta particles.

Gamma rays are the most penetrating form of radiation. A thick shield of lead and concrete will reduce the strength of the gamma rays but will not cpmpletely stop them. This form of radiation will not damage our cells to the same extent as a few alpha or beta particles.
The trouble is, though, many more gamma rays can actually pass through our bodies and attack the DNA in our cells.