Radium radioactive decay

Radon-222 [14859-67-7] Rn, is a naturally occuriing, iaert, radioactive gas formed from the decay of radium-226 [13982-63-3] Ra. Because Ra is a ubiquitous, water-soluble component of the earth s cmst, its daughter product, Rn, is found everywhere. A major health concern is radon s radioactive decay products. Radon has a half-life of 4 days, decayiag to polonium-218 [15422-74-9] Po, with the emission of an a particle. It is Po, an a-emitter having a half-life of 3 min, and polonium-214 [15735-67-8] Po, an a-emitter having a half-life of 1.6 x lO " s, that are of most concern. Polonium-218 decays to lead-214 [15067-28A] a p-emitter haviag = 27 min, which decays to bismuth-214 [14733-03-0], a p-emitter haviag... 

Argon-40 [7440-37-1] is created by the decay of potassium-40. The various isotopes of radon, all having short half-Hves, are formed by the radioactive decay of radium, actinium, and thorium. Krypton and xenon are products of uranium and plutonium fission, and appreciable quantities of both are evolved during the reprocessing of spent fuel elements from nuclear reactors (qv) (see Radioactive tracers). 

Radon A radioactive element, the heaviest of the noble gases, formed by the radioactive decay of radium. 

Although the nucleus of the uranium atom is relatively stable, it is radioactive, and will remain that way for many years. The half-life of U-238 is over 4.5 billion years the half-life of U-235 is over 700 million years. (Half-life refers to the amount of time it takes for one half of the radioactive material to undergo radioactive decay, turning into a more stable atom.) Because of uranium radiation, and to a lesser extent other radioactive elements such as radium and radon, uranium mineral deposits emit a finite quantity of radiation that require precautions to protect workers at the mining site. Gamma radiation is the... 

For the radioactive decay of radium, 2 Ra -late AE in kilojoules when 10.2 g of radium decays. 

The experiment conducted by Rutherford and his co-workers involved bombarding gold foil with alpha particles, which are doubly charged helium atoms. The apparatus used in their experiment is shown in Figure 14-9. The alpha particles are produced by the radioactive decay of radium, and a narrow beam of these particles emerges from a deep hole in a block of lead. The beam of particles is directed at a thin metal foil, approximately 10,000 atoms thick. The alpha particles are delected by the light they produce when they collide with scintilltaion screens, which are zinc sulfide-covered plates much like the front of the picture tube in a television set. The screen... 

Radon gas is the result of the radioactive decay of radium-226, an element that can be found in varying concentrations throughout many soils and bedrock. Figure 31.1 shows the series of elements that begins with uranium-238, and, after undergoing a series of radioactive decays, leads eventually to lead-210. At the time radium decays to become radon gas, energy is released.9 Of all the elements... 

Radon in indoor air arises primarily from radium in the soil. The radon in the soil gas flows under a pressure gradient from the soil into the building. In some cases building practices can lead to high radon levels in the living areas of the house. Radon is chemically quite inert and does not pose a significant radiation health hazard in itself because the retained fraction in the body is so low (Mays et al., 1958). It is, however, an excellent vehicle for the dispersion of its short-lived radioactive decay products. 

In the early years of Theosophy during Blavatsky s lifetime, the modem science that most occupied the movement was, without doubt, the theory of evolution rather than Victorian discoveries in physics and chemistry.4 While Blavatksy in Isis Unveiled and Secret Doctrine grappled in a limited way with modem physics and chemistry, she engaged much more fully with the work of alchemists, especially that of Paracelsus. Her defense of alchemical transmutation was based not upon contemporary science—though she asked of transmutation, Is the idea so absurd as to be totally unworthy of consideration in this age of chemical discovery (Isis 1 503)—but rather upon the exalted reputation of medieval and early modem scientists and alchemists who claimed to have witnessed transmutation (1 503-504). Moreover, the major events that launched modem particle physics—the discoveries of X-rays, the electron, radiation, radium, and radioactive decay—all occurred after Blavatsky died in 1891. 

Marie (NLP 1903, NLC 1911 ) and Pierre (NLP 1903 ) Curie took up further study of Becquerel s discovery. In their studies, they made use of instrumental apparatus, designed by Pierre Curie and his brother, to measure the uranium emanations based on the fact that these emanations turn air into a conductor of electricity. In 1898, they tested an ore named pitchblende from which the element uranium was extracted and found that the electric current produced by the pitchblende in their measuring instrument was much stronger than that produced by pure uranium. They then undertook the herculean task of isolating demonstrable amounts of two new radioactive elements, polonium and radium, from the pitchblende. In their publications, they first introduced the term radio-activity to describe the phenomenon originally discovered by Becquerel. After P. Curie s early death, M. Curie did recognize that radioactive decay (radioactivity) is an atomic property. Further understanding of radioactivity awaited the contributions of E. Rutherford. 

Radium, thorium, and other radionuclides accumulate in uranium mill tailings. The potential environmental effects of these radionuclides has become of increasing concern to the public. In the future, it may be necessary to modify existing uranium recovery processes to accommodate removal of radium and perhaps other radioactive decay products of uranium. 

Marguerite Catherine Perey, an assistant to Marie Curie, is credited with the discovery of francium-223 in 1939. Perey discovered the sequence of radioactive decay of radium to actinium and then to several other unknown radioisotopes, one of which she identified as francium-223. Since half of her sample disappeared every 21 minutes, she did not have enough to continue her work, but a new element was discovered. 

Various radium isotopes are derived through a series of radioactive decay processes. For example, Ra-223 is derived from the decay of actinium. Ra-228 and Ra-224 are the result of the series of thorium decays, and Ra-226 is a result of the decay of the uranium series. 

Radium is extremely radioactive. It glows in the dark with a faint bluish light. Radiums radioisotopes undergo a series of four decay processes each decay process ends with a stable isotope of lead. Radium-223 decays to Pb-207 radium-224 and radium-228decay to Pb-208 radium-226 decays to Pb-206 and radium-225 decays to Pb-209. During the decay processes three types of radiation—alpha (a), beta ((5), and gamma (y)—are emitted. 

ORIGIN OF NAME Originally named "niton" after the Latin word for "shining," it was given the name "radon" in 1923 because it is the radioactive decay gas of the element radium. 

While studying radium, Friedrich Ernst Dorn (1848—1916) found that it gave off a radioactive gas that, when studied in more detail, proved to be the sixth noble gas. Dorn was given credit for its discovery in 1900. He called it radon, a variation of the word radium. Sir Wdham Ramsay and R. W. Whytlaw-Gray, who also investigated the properties of radon, called it niton from the Latin word nitens, which means shining. Several other scientists who worked with radon named it thoron because of the transmutation of radon-220 from the decay of thorium. However, since 1923, the gas has been known as radon because it is the radioactive decay gas of the element radium. The name is derived from the Latin word radius, which means ray. ... 

Radon is a naturally occurring radioactive decay product of uranium. A great deal of attention 222 228 centers around radon, which is the first decay product of radium. Radon and radon... 

In the environment, thorium and its compounds do not degrade or mineralize like many organic compounds, but instead speciate into different chemical compounds and form radioactive decay products. Analytical methods for the quantification of radioactive decay products, such as radium, radon, polonium and lead are available. However, the decay products of thorium are rarely analyzed in environmental samples. Since radon-220 (thoron, a decay product of thorium-232) is a gas, determination of thoron decay products in some environmental samples may be simpler, and their concentrations may be used as an indirect measure of the parent compound in the environment if a secular equilibrium is reached between thorium-232 and all its decay products. There are few analytical methods that will allow quantification of the speciation products formed as a result of environmental interactions of thorium (e.g., formation of complex). A knowledge of the environmental transformation processes of thorium and the compounds formed as a result is important in the understanding of their transport in environmental media. For example, in aquatic media, formation of soluble complexes will increase thorium mobility, whereas formation of insoluble species will enhance its incorporation into the sediment and limit its mobility. 

An unstable parent nucleus may decay into either a stable or an unstable daughter. When the daughter is unstable, which is often the case, the daughter will decay. Often the journey from an unstable nucleus to a stable nucleus involves a long series of steps referred to as a radioactive decay series. One example is the decay series for radium (Figure 17.2). 

Dorn as a product of the radioactive decay of radium. Ramsay made enough of it to measure its properties in 1908. 

Radium is a daughter element, the result of the radioactive decay of long-lived uranium. 

Radon, the heaviest of the noble gases, has been much publicized in recent years because of a fear that low-level exposures increase the risk of cancer. Like astatine and francium, its neighbors in the periodic table, radon is a radioactive element with only a minute natural abundance. It is produced by radioactive decay of the radium present in small amounts in many granitic rocks, and it can slowly seep into basements, where it remains unless vented. If breathed into the lungs, it can cause radiation damage. 

Radium is an element and cannot be metabolized. In biological systems in which radium salts are deposited, these compounds will dissociate based on their solubility in that media. Radioactive decay of the radium cation occurs over time. 

Radium may be transported in the atmosphere in association with particulate matter. It exists primarily as a divalent ion in water, and its concentration is usually controlled by adsorption-desorption mechanisms at solid-liquid interfaces and by the solubility of radium-containing minerals. Radium does not degrade in water other than by radioactive decay at rates that are specific to each isotope. Radium may be readily adsorbed by earth materials consequently, it is usually not a mobile constituent in the environment. It may be bioconcentrated and bioaccumulated by plants and animals, and it is transferred in food chains from lower trophic levels to humans. 

Radium in soils and sediment does not biodegrade nor participate in any chemical reactions that transform it into other forms. The only degradation mechanism operative in air, water, and soil is radioactive decay. Radium has 16 known isotopes (see Chapter 3), but only 4 occur naturally (Radium-223, -224, -226, and -228). The half-life of radium-226 is 1,620 years. The half-lives of radium- 228, radium-223, and radium-224 are 5.77 years, 11.4 days, and 3.64 days, respectively. 

If ps (kg m-3) is the bulk soil density, AR (Bq kg-1) the specific activity of radium in the soil, a the emanating coefficient, and A (s-1) the decay constant of radon, then PsARa atoms, or psARaX Bq of radon, enter the interstitial air per m3 of soil volume per second. At depth in the soil, the rates of entry and radioactive decay of radon are equal, so its activity in interstitial air is... 

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