During the 19th century, chemical science had shown that matter was not continuous but composed of tiny particles particles called atoms.In 1981 G.JohnStone Stoney introduced the word 'electron' as the smallest unit of electrical charge. The laboratory study of electricity through gas by Rontgen 1985 led to the discovery of cathode rays and x-rays. X-rays were formed when the cathode rays(a stream of electrons) struck a solid target in a vacuum tube.Rontengen classified x-rays as electromagnetic radiation, they were man-made by specially designed apparatus.
In 1986 Henri Becquerel found that certain elements possesed the power of emitting rays spontaneously, he called this radioactivity.Becquerel proposed that uranium could spontaneously produce rays which had similar properties to those produce in the laboratory.
Marie Curie followed up the discovery of Becquerel's radioacitivty in 1898. New radioactive elements polonium, radium and atinium were discovered. Detailed investigations of the nature of the rays given off by these elements showed three types of rays. The rays were named alpha, beta and gamma which is still used today.
| Type of Radiation | Nature | Symbol |
|---|---|---|
| Alpha | Two neutrons and two protons | α |
| Beta | High-energy electron | β |
| Gamma | Short wavelength electromagnetic radiation | γ |
| X-ray | A electromagnetic wave with a short wavelength which carries alot of energy | - |