What is Radioactivity?

The isotopes of many atoms are unstable (have extra energy). These are called radioisotopes.

Radioisotopes emit this extra energy (radiation), to become more stable, by splitting up.

When a radioisotope splits up new atoms with different atomic and mass numbers are formed.

Radioisotopes that emit radiation are radioactive. The emission process is called radioactivity.

Radioactivity is a totally random (spontaneous) process. It cannot be predicted.

Losing the Energy

A radioisotope can lose energy by emitting three different types of radiation:

1.

Alpha radiation (often called alpha particles).

2.

Beta radiation (often called beta particles).

3.

Gamma radiation (often called gamma rays).

Alpha Radiation (or alpha particles)

 Alpha particles (given the symbol a ) are:

1.

Made up of two protons and two neutrons (the same as the nucleus of a Helium atom).

2.

Have a mass number of 4 and an atomic number of 2.

3.

Are positively charged.

Beta Radiation (or beta particles)

Beta particles (given the symbol b ) are:

1.

Electrons that are emitted from the nucleus of a radioisotope.

2.

Have almost no mass (the same as an electron).

3.

Are negatively charged.

The animation below shows a Carbon atom (mass number 14 / atomic number 6) emitting energy in beta particle form to give a Nitrogen atom (mass number 14 / atomic number 7). You can see the neutron in the nucleus changing into a proton.

Gamma Radiation (or gamma rays)

Gamma radiation (given the symbol g ):

1.

Is high-energy (short wavelength / high frequency) electromagnetic radiation.

2.

Has no mass.

3.

Has no charge.