Radium abundance

Polonium is a very rare natural element. Uranium ores contain only about 100 micrograms of the element per ton. Its abundance is only about 0.2% of that of radium. 

Radium occurs only in association with uranium (Chapter 31) the observed ratio Ra/U is 1 mg per 3 kg, leading to a terrestrial abundance for Ra of 10 ppm. As uranium ores normally contain only a few hundred ppm of U, it follows that about 10 tonnes of ore must be processed for 1 mg Ra. The total amount of Ra available worldwide is of the order of a few kilograms, but its use in cancer therapy has been superseded by the use of other isotopes, and the... 

The natural occurrence of the group-IIA elements ranges from common to rare e.g., Ca is 5th in the order of atomic abundance of the elements in the earth s crust. Mg is 7th, Ba and Sr are 21st and 22nd, respectively, and Be is 32nd . Radium is of extremely limited availability. It does occur naturally, although it has neither stable nor long-lived radioaetive isotopes it is found in association with U, since ll/2... 

Volpe AM, Olivares JA, Murrell MT (1991) Determination of radium isotope ratios and abundances in geologic samples by thermal ionization mass spectrometiy. Anal Chem 63 913-916... 

ISOTOPES There are no stable isotopes of radium. Radium has 25 known radioisotopes, ranging from Ra-206 to Ra-230. Their half-lives range from a fraction of a second to hundreds of years. Radium-226 was discovered by the Curies and has a half-life of about 1630 years. Ra-226 is the most abundant isotope, and thus, Ra-226 is used to determine radium s atomic mass. 

Radium is the 85th most abundant element found in the Earths crust. Radium is found in the uranium ores pitchblende and chalcolite, which are both very radioactive. Radium metal exists to the extent of only one part to every three million parts of the uranium ore (pitchblende). Only about one gram of radium is found in every seven or eight tons of uranium ore. This scarcity seems to be the reason that only about five pounds of uranium are produced each year in the entire world. Uranium ores are found in the states of Utah, New Mexico, and Colorado in the United States and in Canada, the Czech Republic, Slovakia, Russia, Zaire, and France. 

Radiums most important use is as a source of radiation in industry, medicine, and laboratories. The isotope radium-226, which is the most abundant of all the 25 isotopes and has a half-life of 1630 years, is the only useful form of the element. It is used in the medical treatment of malignant cancer growth. It kills cancer cells that have spread throughout the body. 

Radium is an intermediate member of the uranium decay series. Therefore, it is present in all uranium minerals. Its abundance in uranium is calculated to be about 0.33ppm. 

At the time of the discovery of radio-activity, about seventy-five substances were called elements in other words, about seventy-five different substances were known to chemists, none of which had been separated into unlike parts, none of which had been made by the coalescence of unlike substances. Compounds of only two of these substances, uranium and thorium, are radio-active. Radio-activity is a very remarkable phenomenon. So far as we know at present, radio-activity is not a property of the substances which form almost the whole of the rocks, the waters, and the atmosphere of the earth it is not a property of the materials which constitute living organisms. It is a property of some thirty substances—of course, the number may be increased—a few of which are found widely distributed in rocks and waters, but none of which is found anywhere except in extraordinarily minute quantity. Radium is the most abundant of these substances but only a very few grains of radium chloride can be obtained from a couple of tons of pitchblende. 

The rarity of polonium is evident from a calculation (1) which shows that the outermost mile of the earth s crust contains only 4000 tons of the element, whereas radium, usually classed as rare, is present to the extent of 1.8 X 107 tons. The abundance of polonium in uranium ores is only about 100 Mg per ton and hence separation of the element from such mineral sources cannot seriously be considered. However, radium, at equilibrium with its daughters, contains 0.02 wt % of polonium and, until recently, most of the element was obtained either from radium itself or, more usually, from expended radon ampoules which, after the radon decay is complete, contain radium-D and its daughters. Fortunately, however, the parent of polonium in these sources, bismuth-210, can be synthesized by neutron bombardment of natural bismuth [Bi209 (n,y) Bi210] and with the advent of the nuclear reactor it has become practicable to prepare milligram amounts of polonium. Almost all of the chemistry of the element recorded in the recent literature has been the result of studies carried out with polonium-210 prepared in this way. 

Strontium has four naturally occurring isotopes (Table 4.2). It is a member of the alkaline earths (Group 2A) along with beryllium, magnesium, calcium, barium, and radium (Fig. 2.4). Strontium substitutes for calcium and is abundant in minerals such as plagioclase, apatite, and calcium carbonate. 

The half-life (Eq. 9-4) determines the isotopic abundance needed to achieve a given radiation rate, a practical matter in providing a sufficient rate of decay to permit counting with an acceptably low statistical error. Even very short-lived isotopes such as 13N, have proved useful as tracers.13 The amount of an isotope giving 3.7 x 1010 disintegrations per second (this is 1 g of pure radium, 0.3 mg of 3H, or 0.22 g of 14C) is known as the curie (Ci). One milli-curie (mCi) provides 2.22 x 109 disintegrations / min... 

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. 

The metals of most concern are the heavy metals, especially cadmium, lead, and mercury. Although it is a metalloid with characteristics of both metals and nonmetals, arsenic is commonly classified as a heavy metal for a discussion of its toxicity. Though not particularly toxic, zinc is abundant and may reach toxic levels in some cases. For example, zinc accumulates in sewage sludge and crop productivity has been lowered on land fertilized with sludge because of zinc accumulation. Copper may be toxic to plants. Aluminum, a natural constituent of soil, may be leached from soil by polluted acidic rainwater and reach levels that are toxic to plants. Other metals that may be of concern because of their toxicides include chromium, cobalt, iron, nickel, and vanadium. Radium, a radioactive alpha particle-emitting metal, can be very toxic at even very low levels in water or food. 

The moderately abundant heavier elements are found principally as sulphates SrS04 and BaS04, whereas beryllium is rather rare and occurs in beryl Be3Al2Si6018. Radium is radioactive, its longest-lived... 

Except for radium, the elements are widely distributed in minerals and in the sea. They occur in substantial deposits such as dolomite (CaC03-MgC03), camallite (MgCl2-KCl-6H20), and barytes (BaS04). Calcium is the third most abundant metal terrestrially. 

Helium is the second most abundant element in the universe. In the Earth, it is continuously formed by radioactive decay, mostly of uranium and thorium. Its present concentration in the atmosphere is probably the equilibrium concentration between the amount being released from the Earth s crust and the amount of hehum escaping from the atmosphere into space. The atmosphere represents the major source for neon, argon, krypton, and xenon. They are produced as by-products during flactional distillation of liquid air. Radon is obtained from the radioactive decay of radium. 

Asia. Large rivers of Asia are clearly the less well documented in terms of trace-element concentrations. This is mainly due to their low abundances of trace elements, probably related to their high pH character. A couple of studies have focused on the riverine input of metals to the Arctic and Pacihc oceans. Himalayan rivers have not been documented for REEs (except the Indus river), but have been analyzed for particular elements such as strontium, uranium, osmium, and radium. There is clearly a need for data on trace elements in the rivers of Asia, particularly in the highly turbid peri-Himalayan rivers. 

Barium is a member of the alkaline earth metals. The alkaline earth metals make up Group 2 (IIA) of the periodic table. The other elements in this group are beryllium, magnesium, calcium, strontium, and radium. These elements tend to be relatively active chemically and form a number of important and useful compounds. They also tend to occur abundantly in Earth s crust in a number of familiar minerals such as aragonite, calcite, chalk, limestone, marble, travertine, magnesite, and dolomite. Alkaline earth compounds are widely used as building materials. 

The amount of radium in Earth s crust is very small. Its abundance has been estimated to be about 0.0000001 parts per million. It occurs not only in pitchblende, but in all ores that contain uranium. It is formed when uranium gives off radiation and breaks down. 

The abundance of radon in air is too small to be estimated. Some radon is always present because it is formed during the breakdown of uranium and radium. The abundance of radon in Earth s crust is estimated to be the lowest of any chemical element. 

The alkaline earth metals show a wider range of chemical properties than the alkali metals. The IIA metals are not as reactive as the lA metals, but they are much too reactive to occur free in nature. They are obtained by electrolysis of their molten chlorides. Calcium and magnesium are abundant in the earth s crust, especially as carbonates and sulfates. Beryllium, strontium, and barium are less abundant. All known radium isotopes are radioactive and are extremely rare. 

An asterisk denotes a radioactive isotope whose lifetime is indicated in the column Natural abundance. When a stable element has several radioactive isotopes, a few ones have been chosen for their interest in different applications. For the radioactive elements, only the isotopes with the longest lifetimes and at least one with a nonzero nuclear spin I are indicated. The electronic configuration of an element with atomic number Z is given in italics in the Name and symbol column. When relevant, the old Group label notation of the periodic table is indicated in brackets in this same column. The radioactive elements francium, radium, and actinium (Z = 87, 88, and 89, respectively) have been omitted. 

In general, radium in rock does not pose a health risk, but there are situations where radium is found in unusual abundance, and care must be taken with human exposure. Oil fields, coal mines, and phosphate mines generate hazardously high concentrations of radium as uranium and thorium deposits are disturbed underground. In Poland, for example, radium-containing water that was discharged from coal mines has been... 

The half-life of radium 226 makes its abundance in the upper layers of ocean sediments, which settled within the past 10,000 years (Holocene epoch), convenient to measure. A comparison of 226Ra abundance to 228Ra in various ocean locations allows for determination of ocean current directional flow Because 228Ra is produced more strongly in shallow areas, and its lifetime is so much shorter, observation of radium 228 far from shore can indicate offshore currents that are otherwise difficult to measure. 

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