The atoms of some chemical elements are unstable. They try
to rearrange themselves to make more stable atoms. In the process, they give
off radiation particles or tiny bursts of radiation. This process is called
radioactivity. Although radioactivity can be harmful to people, it can also be
important to us in everyday life. It is used to make nuclear energy and
preserve food, and it also plays a vital role in the treatment of
cancer.
Some types of radioactivity are harmful, because they damage or
destroy the tissues of the human body. If people receive large doses of
radioactivity, they can become ill with radiation sickness, which often causes
cancer. Radiation sickness can also affect people’s ability to have
children.
The three types of radiation are alpha and beta particles, and gamma
radiation, named after the Greek letters above. An alpha particle is two
protons joined to two neutrons. A beta particle is an electron. Gamma radiation
is high-energy electromagnetic radiation.
An alpha particle is made when the nucleus (central part) of a
large, unstable atom rearranges itself, or decays, to make a smaller, more
stable atom. The new and smaller atom has two protons and two neutrons fewer
than the original atom. These join together to make the alpha particle that is
given off. Some energy is also released as a gamma ray. This is high-energy and
high-frequency radiation, travelling at the speed of light.
Beta decay is quite different from alpha decay. One of the
neutrons in the nucleus of the unstable atom changes into a proton and an
electron. The proton joins onto the nucleus, but the electron is ejected from
the atom at high speed. This fast-moving electron is called a beta particle.
Some energy is also released as a gamma ray.
Radioactivity can cause cancer if it harms healthy cells in the
human body. It can also help to cure cancer if it is used to destroy unhealthy
cells. In radiotherapy, a powerful machine fires carefully targeted beams of
radiation at tumours (cancer cells) in the patient’s body. The
radioactivity destroys the cells and helps to improve the patient’s
chances of survival.
