Encyclopedia > Alpha particle

  Article Content

Alpha particle

Alpha particles or alpha rays are a form of particle radiation which are highly ionizing and have low penetration. They consist of two protons and two neutrons bound together into a particle that is identical to a helium nucleus, and can be written as He2+. In contrast to beta decay, Alpha decay is mediated by the strong nuclear force.

Alpha particles are emitted by radioactive nuclei such as uranium or radium in a process known as alpha decay. This sometimes leaves the nucleus in an excited state, with the emission of a gamma ray removing the excess energy.

Alpha rays are easily absorbed by materials and can travel only a few centimeters in air. They can be absorbed by tissue paper or the outer layers of human skin and so are not generally dangerous to life unless the source is ingested or inhaled. If Alpha radiation does enter the body, however, they are the most dangerous form of ionising radiation. They are the most strongly ionising, and with large enough doses can cause any or all of the symptoms of radiation poisoning.

See also: radioactivity, cosmic rays, nuclear physics, radioactive isotopes, radioactive decay

All Wikipedia text is available under the terms of the GNU Free Documentation License

  Search Encyclopedia

Search over one million articles, find something about almost anything!
  Featured Article
308 BC

...     Contents 308 BC Centuries: 5th century BC - 4th century BC - 3rd century BC Decades: 350s BC 340s BC 330s BC 320s BC 310s BC 300s BC 290s BC 280s BC 270s ...