Earth radium

The seventh period of the periodic table is occupied by a similar series called the actinide series. Beginning with actinium the 5/ electron shell is populated in a matmer analogous to filling the 4/ electron shell in the lanthanide series. A suggested electronic configuration [K2, M6], is shown in Table 9.2. After the alkaline earth radium, additional electrons are added to the 6d and 5/ shells, beginning the actinide series. At the beginning of the actinide series electrons are added... 

The elements in Group II of the Periodic Table (alkaline earth metals) are. in alphabetical order, barium (Ba). beryllium (Be), calcium (Ca). magnesium (Mg), radium (Ra) and strontium (Sr). 

Gr. aktis, aktinos, beam or ray). Discovered by Andre Debierne in 1899 and independently by F. Giesel in 1902. Occurs naturally in association with uranium minerals. Actinium-227, a decay product of uranium-235, is a beta emitter with a 21.6-year half-life. Its principal decay products are thorium-227 (18.5-day half-life), radium-223 (11.4-day half-life), and a number of short-lived products including radon, bismuth, polonium, and lead isotopes. In equilibrium with its decay products, it is a powerful source of alpha rays. Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300-degrees G. The chemical behavior of actinium is similar to that of the rare earths, particularly lanthanum. Purified actinium comes into equilibrium with its decay products at the end of 185 days, and then decays according to its 21.6-year half-life. It is about 150 times as active as radium, making it of value in the production of neutrons. 

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... 

R. Patel and D. Clifford, Radium Removalfrom Water by Manganese Dioxide Adsorption and Diatomaceous Earth Filtration, NTIS PB92-115260/AS, Springfield, Va., 1992. 

Barium [7440-39-3] Ba, is a member of Group 2 (IIA) of the periodic table where it Hes between strontium and radium. Along with calcium and strontium, barium is classed as an alkaline earth metal, and is the densest of the three. Barium metal does not occur free in nature however, its compounds occur in small but widely distributed amounts in the earth s cmst, especially in igneous rocks, sandstone, and shale. The principal barium minerals are barytes [13462-86-7] (barium sulfate) and witherite [14941-39-0] (barium carbonate) which is also known as heavy spar. The latter mineral can be readily decomposed via calcination to form barium oxide [1304-28-5] BaO, which is the ore used commercially for the preparation of barium metal. 

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... 

When Z gets big enough, no number of neutrons is enough to stabilize the nucleus. Notice in Figure 2-20 that there are no stable nuclei above bismuth, Z — 83. Some elements with higher Z are found on Earth, notably radium (Z = 88), thorium (Z = 90), and uranium (Z = 92), but all such elements are unstable and eventually disintegrate into nuclei with Z < 83. Consequently, the set of stable nuclei, those that make up the world of normal chemistry and provide the material for all terrestrial chemical reactions, is a small subset of all possible nuclei. 

Between barium (Group 2, element 56) and lutetium (Group 3, element 71), the 4f orbitals fill with electrons, giving rise to the lanthanides, a set of 14 metals named for lanthanum, the first member of the series. The lanthanides are also called the rare earths, although except for promethium they are not particularly rare. Between radium (Group 2, element 88) and lawrenclum (Group 3, element 103), are the 14 actinides, named for the first member of the set, actinium. The lanthanides and actinides are also known as the inner transition metals. 

Krishnaswami S, Graustein WC, Turekian KK, Dowd F (1982) Radium, thorium, and radioactive lead isotopes in groundwaters application to the in-situ determination of adsorption-desorption rate constants and retardation factors. Water Resour Res 6 1663-1675 Krishnaswami S, Bhushan R, Baskaran M (1991) Radium isotopes and Rn in shallow brines, Kharaghoda (India). Chem Geol (Isot Geosci) 87 125-136 Kronfeld J, Vogel JC, Talma AS (1994) A new explanation for extreme " U/ U disequilibria in a dolomitic aquifer. Earth Planet Sci Lett 123 81-93... 

Bhat SG, Krishnaswami S (1969) Isotopes of uranium and radium in Indian rivers. Proc Ind Acad Sci Earth Planet Sci 70 1-17... 

Moore DG (1967) Amazon and Mississippi River concentrations of uranium, thorium, and radium isotopes. Earth Planet Sci Lett 2 231-234... 

McKee BA, DeMaster DJ, Nittrouer CA (1986b) The use of " Th/ U disequilibrium to examine the fate of particle-reactive species on the Yangtze continental. Shelf. Earth Planet Sci Lett 68 431-442 McKee BA, DeMaster DJ, Nittrouer CA (1987) Uranium geochemistry on the Amazon shelf evidence for uranium release from bottom sediments. Geochim Cosmochim Acta 51 2779-2786 Miller RJ, Kraemer, TF, McPherson BF (1990) Radium and radon in Charlotte Harbor estuaiy, Florida. Estuar Coastal Shelf Sci 31 439-457... 

Radon is a naturally occurring, chemically inert, radioactive gas. It is colorless, odorless, and tasteless. It is part of the uranium-238 decay series, the direct decay product of radium-226. Radon moves to the earth s surface through tiny openings and cracks in soil and rocks. High concentrations of radon can be found in soils derived from uranium-bearing rocks, such as pitchblende and some... 

Calcium, strontium, barium and radium, the alkaline earth metals proper, are the typical elements of the 2nd column (the 2nd group) of the Periodic Table. 

Beryllium and magnesium belong to the 2nd group of the Periodic Table together with calcium, strontium, barium and radium. Characteristic differences, however, may be noticed between the chemistry of Be and Mg and that of the alkaline earth s proper. Be has a unique chemical behaviour with a predominantly covalent character. The heavier elements (Ca, Sr, Ba, Ra) have a predominant ionic behaviour in their compounds. Mg has a chemistry in a way intermediate but closer to that of Be. Analogies between the Mg and Zn chemistries may also be underlined. 

Radium is the last element in group 2 and is very similar to the other alkali earth metals, which makes it the largest and heaviest element in the group. It particularly resembles barium, which is just above it in group 2 of the periodic table. Radium is a bright white radioactive luminescent alkali earth metal that turns black when exposed to air. Its melting point is 700°C, its boiling point is 1,140°C, and its density is approximately 5.0 g/cm. ... 

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. 

Radium, like the other alkali earth metals, readily combines with halogens such as chlorine and bromine (which are electronegative). RaCl and RaBr are the forms in which radium is usually stored and shipped for a variety of uses. 

Radium hydroxide (RaOH) is the most soluble of all the hydroxides of the alkali earth metals. It is formed when radium reacts with water (2Ra + lUjO —> 2RaOH + H T). 

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