The spontaneous emission of different types of radiations by unstable heavy nucleus is called radioactivity. As the atomic number goes on increasing the binding energy per nucleon goes on decreasing, so the atomic nucleus emit different particles such as α, β, γ particles to gain stability. This process of emitting particles is known as radioactivity. Those substances which shows the phenomenon of radioactivity is called radioactive substance.
Henri Becquerel, Professor of Physics at the University of Paris, discovered that uranium salts could penetrate a photographic plate even if the plate was covered. He realized that the salts were emitting some form of radiation that could pass through the wrapping. He also found that this radiation could ionize a gas, causing a charged electroscope to discharge. In this way, after a series of experiments, he concluded that uranium emits penetrating charged particles and he named this phenomenon as radioactivity. He is also called the father of radioactivity and the unit of radioactivity is named as Becquerel in his honor.
Uranium, thorium, polonium, radium are some of the radioactive elements.
Types of radioactivity: Radioactivity is generally divided into two types:
1. Natural radioactivity: The phenomenon of spontaneous emission of highly penetrating radiations from the naturally occurring heavy elements is called radioactive elements. It cannot be controlled by changing the physical phenomena such as pressure, hear, temperature etc.
2. Artificial Radioactivity: The phenomenon of inducing the radioactivity by artificial means through nuclear transmutation is called artificial radioactivity. A stable compound is made radioactive by bombarding the high energy particle. Lighter elements can also exhibit this radioactivity. It can be controlled by controlling the speed of the bombarding projectiles.
Uses of radioactivity:
- It is used to detect the cracks in metal on airplanes.
- It is used in treating the cancer patients.
- It is used in detection of age of the substance through carbon dating.
- It is used for preservation of food grains and seeds.
- It is used to sterlize the surgical instrument.
- It is also for preparing synthetic elements.