Radioactivity in Chemistry
A phenomenon of spontaneous disintegration, first observed in certain naturally occurring heavy elements like radium, actinium, uranium, thorium, etc, with the emission of alpha, beta and gamma rays.
It is the property of the nuclide to disintegrate in which a transformation takes place of a relatively unstable nuclide to relatively stable nuclide accompanied with the emission of particles or electromagnetic radiation.
The nuclide that decays is said to be radioactive.
Discovery of Radioactivity
The phenomenon was accidentally discovered in 1896 by French physicist Henry de Becquerel.
He observed that uranium mineral gave off invisible radiation. He termed this property of uranium radioactivity. Later Pierre and Madam Curie showed similar phenomenon in other metals like poeonium, francium and radium.
(i) Sub – Atomic Particles (Radiation)
- Alpha (α) Particles : A positively charged helium atom which has very little penetrating power. They can be absorbed by a sheet of paper or stopped by aluminium foil.
- Beta (β) Particles : A negatively charged light particle. Its penetrating power is greater than that of alpha – ray.
(ii) Penetrating Particles (Radiation)
Also called Gamma (γ) emission. These are electromagnetic radiations of low wavelength, high frequency, and high energy. Their penetrating power is very great as they can pass through several centimetre of lead.
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