Introduction to Radioactivity

Antoine Henri Becquerel, a French scientist, 1896, was conducting an experiment which started with the exposure of a uranium-bearing crystal to sunlight. Once the crystal had sat in the sunshine for a while, he placed it on a photographic plate. As he had anticipated, the crystal produced its image on the plate. Becquerel theorized that the absorbed energy of the sun was being released by the uranium in the form of x-rays. The husband and wife team of Pierre and Marie Curie in 1898 became interested in Becquerel’s discovery. While experimenting with their own uranium-containing ore, they came up with the term “radioactivity” to describe the spontaneous emissions that they studied. This word is still used today to describe this special characteristic of some elements (radioisotopes).

While comparing the activity of pure uranium to a uranium ore sample, they found that the ore was significantly more radioactive than the pure material. They concluded that the ore contained additional radioactive components besides the uranium. This observation led to the discovery of two new radioactive elements which they named polonium and radium.

Radioactivity is the spontaneous disintegration of atomic nuclei. In other word, Radioactivity is the energy and mass released by spontaneous changes in the nucleus of an atom.

Radiation is energy that travels (‘radiates’) as waves or particles. Heat, light, sound, microwaves, radar, radio waves, X-rays, alpha and beta particles, and gamma rays are all forms of radiation.

All substance is made of atoms. These have electrons (e) around the outside, and a nucleus in the middle. The nucleus consists of protons (p) and neutrons (n), and is extremely small. In some types of atom, the nucleus is unstable, and will decay into a more stable atom.

Unstable atomic nuclei will spontaneously decompose to form nuclei with a higher stability. The decomposition process is called radioactivity. The energy and particles which are released during the decomposition process are called radiation. When unstable nuclei decompose in nature, the process is referred to as natural radioactivity. When the unstable nuclei are prepared in the laboratory, the decomposition is called induced radioactivity.