 |
|
One Hundred Years of Radioactivity
|
|
 Radioactivity is the spontaneous emission of penetrating rays by an unstable atomic nucleus which is subsequently transformed into a different nucleus (different mass). The rays that are emitted are alpha (and beta particles, and gamma rays. In 1896, Antoine-Henri Becquerel discovered radioactivity when he noticed that a photographic plate had been exposed after some uranium salt was left next to it. The uranium salt was spontaneously emitting a penetrating type of radiation which he called "uranic radiation". After Becquerel's discovery of radioactivity, many more discoveries and advancements have occurred.
In 1898, Marie Curie and her husband Pierre discovered their first radioelement which they called polonium. Later that year, the Curies also reported the existence of radium. In 1903, Becquerel and the Curies were both awarded the Nobel Prize in Physics for their work on radioactivity Marie Curie was awarded the 1911 Nobel Prize in Chemistry for the discovery of polonium and radium.
In the late 1890s Ernest Rutherford and his partner Frederick Soddy found that radioactivity was made up of alpha and beta particles. Rutherford was awarded the 1908 Nobel Prize in Chemistry for his investigations into radioactivity. In 1911, Rutherford proposed the nuclear model of the atom which is the same model that is used today and what he is best known for. The model describes the atom as containing a nucleus which has most of the mass, all of the positive charge, and is situated in the center of the atom.
In 1934 Irène Curie (Marie and Pierre Curie's daughter) and her husband Frédéric Joliot discovered how to create new artificially radioactive forms of matter . This important discovery enabled the production of new radioisotopes such as phosphorus-30, nitrogen-13, iron-59, cobalt-60, iodine-131, technetium-99, cesium-137, and plutonium-239. Plutonium-239 was an important discovery because it is fissionable and consequently, is used as the explosive material in the atomic bomb.
Radioactivity is mainly known for its use in weapons and nuclear reactors. However, the study of solar neutrinos, the treatment of cancer (cobalt-60), radiocarbon dating (carbon-14), and nuclear medicine (treatment and diagnoses) also utilize radioactivity. For instance, iodine-131 is used to diagnose and treat thyroid disease. Technetium-99 is used to diagnose thyroid, bone, liver, spleen, lung, cardiovascular, brain and kidney disorders. Carbon-11, nitrogen-13, and oxygen-15, fluorine-18, and bromine-75 are used in positron emission tomography (PET). PET, a growing field in nuclear medicine, is a noninvasive diagnostic technique that takes 3-dimensional images in vivo.
As medical science continues to advance, new and beneficial uses for radioactive elements are anticipated.
|
