Radioactivity

Radioactivity

The nuclei of some atoms spontaneously disintegrate from one form of isotope to another until they reach a stable form. These atoms emit particles (alpha & beta) & photons (gamma rays) which are different in charge, size, penetrating power and ionization energy.

Half life of the isotope

The half - life of an isotope is the time needed to decay until half of it's mass remains. Here is an example. 50 grams of the radioactive isotope Carbon 14 with a half-life of 5,730 years after 5,730 years, 25 grams will remain. After another 5,730 years only 12.5 grams will remain and so on. When a radioactive isotope completely decays into a daughter isotope, it may decay into another isotope, or remain the same, depending on whether it is stable or radioactive.

Types of decay

There are three main types of radioactive decay; these include Alpha, Beta, & Gamma Radiation. Alpha and Beta decay are released in particles, while Gamma radiation is released in rays.

Gamma radiation is more penetrating than alpha & beta. An alpha particle can be stopped by a thin piece of paper and a beta particle can be stopped by a sheet of aluminium foil Gamma radiation can penetrate both with ease. The most efficient way to stop gamma rays is with and apron of lead (hence the wearing of a lead covering when you get a dental X-Ray).

Alpha particles are completely stopped by a sheet of paper, beta particles by an aluminum plate. Gamma rays however, can only be reduced by much more substantial obstacles, such as a very thick piece of lead.

Here are some common radiation emitters:

• Alpha

Americium-241

Radon

• Beta

Strontium-90

• Gamma

Uranium-238

Example of alpha decay

• ${}_{88}^{226}Ra$
• ${}_{86}^{222}Rn$
• ${}_{2}^{4}He$

See also

• Atomic Structure
• Age of the Earth - practical application of radioactive decay

Additional resources

• w: Isotope lists, 97+