Radioactive Decay

Radioactive decay is the spontaneous disintegration of the nucleus of an atom which results in the emission of particles.

  • Spontaneous Process: Cannot be speed up or slowed down by physical means(changes in pressure or temperature or the decay of other atoms). It is not affected by any chemical condition or the chemical compound that it exists in.
  • Random Process: Radiation is emitted at random. It is impossible to predict which nucleus and when any particular nucleus will disintegrate.

A radioactive nucleus consists of an unstable assembly of protons and neutrons which becomes more stable by emitting an alpha, a beta particle or a gamma photon.

Evidence of randomness of radioactive decay

  • Can be demonstrated by observing the fluctuations in count rate of a Geiger-Muller (GM) tube
  • When a GM tube is near a radioactive source, the irregularity of the counts and the fluctuations in the count rate recorded by the GM tube show the randomness of radioactive decay.
  • At any moment, each parent nucleus has the same chance of decaying, but we do not know which are the ones that will decay, nor do we know when they will decay.

Types of radiation

  • Alpha particles
  • Beta particles
  • Gamma rays


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