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The rate at which a radioactive element decays is expressed in terms of its half-life ; i. The product of a radioactive decay process—called the daughter of the parent isotope—may itself be unstable, in which case it, too, will decay. The process continues until a stable nuclide has been formed. Such charged atoms are called ions. The neutral helium atom has two electrons outside its nucleus balancing these two charges. The beta plus particle, also called the positron , is the antiparticle of the electron; when brought together, two such particles will mutually annihilate each other.

Gamma rays are electromagnetic radiations such as radio waves, light , and X-rays. In the less common forms of radioactivity, fission fragments , neutrons, or protons may be emitted.

Fission fragments are themselves complex nuclei with usually between one-third and two-thirds the charge Z and mass A of the parent nucleus. Neutrons and protons are, of course, the basic building blocks of complex nuclei, having approximately unit mass on the atomic scale and having zero charge or unit positive charge, respectively.

The neutron cannot long exist in the free state. It is rapidly captured by nuclei in matter; otherwise, in free space it will undergo beta-minus decay to a proton , an electron, and an antineutrino with a half-life of The proton is the nucleus of ordinary hydrogen and is stable.

Guest Contribution: A Discussion on Radiation and Radioactive Material

Familiar types of electromagnetic radiation include sunlight cosmic radiation , x-rays , radar, and radio waves. The other form of radiation — known as particle radiation — is tiny fast-moving particles that have both energy and mass weight.

Radiation vs Radioactive Atoms

This less-familiar form of radiation includes alpha particles , beta particles , and neutrons , as explained below. As previously indicated, large unstable atoms become more stable by emitting radiation to get rid of excess atomic energy radioactivity. This radiation can be emitted in the form of positively charged alpha particles , negatively charged beta particles , gamma rays , or x-rays , as explained below. Through this process — called radioactive decay — radioisotopes lose their radioactivity over time. This gradual loss of radioactivity is measured in half-lives.

Essentially, a half-life of a radioactive material is the time it takes one-half of the atoms of a radioisotope to decay by emitting radiation. This time can range from fractions of a second for radon to millions of years for thorium When radioisotopes are used in medicine or industry, it is vital to know how rapidly they lose their radioactivity, in order to know the precise amount of radioisotope that is available for the medical procedure or industrial use.

In some elements, the nucleus can split as a result of absorbing an additional neutron, through a process called nuclear fission.

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Such elements are called fissile materials. One particularly notable fissile material is uranium This is the isotope that is used as fuel in commercial nuclear power plants.

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When a nucleus fissions, it causes three important events that result in the release of energy. Specifically, these events are the release of radiation, release of neutrons usually two or three , and formation of two new nuclei fission products. Radiation can be either ionizing or non-ionizing, depending on how it affects matter. Non-ionizing radiation includes visible light, heat, radar, microwaves, and radio waves.

This type of radiation deposits energy in the materials through which it passes, but it does not have sufficient energy to break molecular bonds or remove electrons from atoms.

Radioactive decay - Wikipedia

By contrast, ionizing radiation such as x-rays and cosmic rays is more energetic than non-ionizing radiation. Consequently, when ionizing radiation passes through material, it deposits enough energy to break molecular bonds and displace or remove electrons from atoms. This electron displacement creates two electrically charged particles ions , which may cause changes in living cells of plants, animals, and people. People working with or near radiation sources are protected by barriers which include shielding of lead, concrete, and other heavy materials.

Protective clothing provides protection against some types of radiation. People who work near radioactive materials routinely wear devices called dosimeters. These devices monitor and record ionising radiation doses to guard against the possibility of over exposures. What to do when there is an imminent radiation hazard? In an accident, a lot of radioactive iodine may be released into the air.

Most of the inhaled iodine is stored in the thyroid gland. Hence the thyroid gland receives a considerably high radiation dose. The radiation emitted by radioactive iodine may cause tumours or hypofunction in the thyroid gland. The accumulation of radioactive iodine in the thyroid gland can be efficiently reduced by taking a iodine tablet at the right moment. Non-radioactive potassium iodine saturates the thyroid gland.

Consequently, radioactive iodine cannot be absorbed in the thyroid gland. Radioactive iodine is passed from the body with urine. The tablet should be taken 1 — 6 hours before the radioactive cloud is transferred to the area. One iodine dose provides protection for about 24 hours.

Radioactive materials contain elements whose atoms are unstable changeable and emit energy in the form of ionising radiation. There are two sources of radioactive materials, those that are naturally occurring i. Radiation Protection It has long been recognized that large doses of ionizing radiation can damage human tissues. Over the years, as more was learned, scientists became increasingly concerned about the potentially damaging effects of exposure to large doses of radiation. The need to regulate exposure to radiation prompted the formation of a number of expert bodies to consider what needs to be done.

What is radiation? How do we use radiation? Quick Links What is Nuclear Energy? Emergency Planning. Nuclear Security. International Cooperation.

  • The History of Radiation.
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  • Types of Radioactive Emissions.

Career Opportunities. Contact Us. Report a Safety Concern. Fraud Alert. Alpha Radiation Alpha particles consist of two protons and two neutrons, and carry a positive charge. Beat Radiation Beta radiation consists of fast moving electrons ejected from the nucleus of an atom. X-Rays X-rays are a form of radiation produced mainly by artificial means rather than by naturally occurring radioactive substances.

Gamma Radiation Gamma radiation is a very penetrating type of radiation. Neutrons Less common, neutron radiation occurs when neutrons are ejected from the nucleus by nuclear fission and other processes. Time The shorter the period of exposure to radiation, the less radiation will be absorbed.