PHYSICS - What Are Radioactive Isotopes - Properties of Matter

The identity and chemical properties of any atom are determined by the number of protons in its nucleus. As atoms get bigger and heavier, the nuclei get bigger and heavier and the protons need a “nuclear glue” to help hold them together. Neutrons provide this glue and prevent the positive charges of protons from repelling each other, thanks to something called the strong nuclear force. Elements can exist with slightly different numbers of neutrons. We call these isotopes of an element. The number of protons in isotopes of one element will always be the same; this means that the element is unchanged and so will react chemically in exactly the same way. There is often more than one stable isotope of an element. Much of the world around us is made up of stable isotopes. However, sometimes there aren’t enough neutrons in a nucleus or there are too many for it to be stable. Nuclei will try to stabilise themselves. If there are too many protons or too many neutrons, the nucleus can spontaneously rearrange itself and throw out particles in the process. This is essentially what happens in radioactive decay. Isotopes that have unstable nuclei are known as radioactive isotopes or radioisotopes. The more unstable a nucleus, the faster it will try to rearrange itself into a more stable state. This is known as radioactive decay. Radioisotopes are often used in medicine to trace aspects of body chemistry or blood flow. Atoms of radioisotopes can act as “markers”, allowing chemists to follow how a reaction sequence occurs. Radioisotopes are also used in radiotherapy to kill malignant cancer cells.