Chemistry - Radioactivity


  • The process of emission of particles from nuclei because of the nuclear instability; is known as radioactivity.

  • The substance that releases such energy/rays is known as radioactive substance.

  • The invisible rays released from such radioactive substance are known as radioactive rays.

  • Likewise, radioactivity is a nuclear phenomenon that happens (naturally) because of the nuclear instability of atoms.

  • In 1896 Henri Becquerel first observed the phenomena of radioactivity, but the term ‘radioactivity’ was coined by Marie Curie.

  • Marie Curie discovered the radioactive elements namely Polonium and Radium in 1898.

  • For her discovery, Marie Curie won the Nobel Prize.

Radioactive Rays

  • After long years of experiment, Ernest Rutherford along with his colleague (Hans Geiger and his student Ernest Marsden), discovered alpha rays, beta rays, and gamma rays.

  • These rays emitted as the result of the disintegration of atoms.

Alpha (α) Particles

  • Alpha particles are usually composed of two protons and two neutrons, which are tightly bound together.

  • Alpha particles are being released during radioactive decay (or alpha decay) from the nucleus radio nuclides.

  • The alpha particles are identical to the nucleus of either normal helium atom or doubly ionized helium atom.

  • In comparison to other particles (i.e. Gamma and Beta), alpha particles are heavy and slow. Therefore, alpha particles have very small range in the air.

  • Because of slow speed, Alpha particles have very weak penetrating powers; these particles are even stopped by a thin paper sheet (see image given above).

  • Because of having the double positive charge, alpha particles are highly ionizing.

Beta (β) Particles

  • Beta particles are the fast moving electrons emitted by some radio nuclides during the radioactive decay (also known as beta decay).

  • Beta particles are of much lighter weight and carry a single negative charge.

  • Beta particles are rarely ionizing than the alpha particles.

  • Because of having lighter weight, beta particles can travel much farther than alpha particles; however, beta particles can be stopped by several sheet of papers or one sheet of aluminum.

  • Beta particles are negatively charged and get attracted towards positively charged particles.

Gamma (ү) Particles

  • Gamma particles are the bundle of high energy namely electromagnetic energy (photon) emitted by the radioactive elements during the radioactive decay.

  • Among all three particles (alpha, beta, and gamma), gamma particles are the most energetic photons.

  • Gamma particles, which are the form of electromagnetic radiation(EMR), originate from the nucleus.

  • The wavelengths of gamma are the shortest among all three.

  • Gamma particles have no charge and they are neutral; therefore, they are unaffected by magnetic and electric fields.

Uses of Radioactive Elements

  • Radioactive elements are used in −

    • Medical field (treatment of many diseases)

    • Industrial process

    • Energy production – Nuclear reactors