Alkaline radium

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). 

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. 

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. 

The chemistry of radium is very similar to its Group IIA alkaline-earth analog harium. The metal forms a number of salts in its +2 valence state, the only valence state typical of all alkaline earth metals. The few salts that are of commercial use include chloride, RaCb, bromide RaBr2, and sulfate, RaS04. 

Complexes with organic compounds have been reported. Solubility studies with tributyl phosphate (TBP) indicate the formation of a complex PoC14-2TBP (IS). Weighable amounts of polonium tetrachloride in dilute hydrochloric acid can be titrated to a colorless end point with ethylene-diamine tetra-acetic acid (EDTA) the results suggest a complex with two molecules of EDTA, but solubility studies favor a 1 1 complex. The EDTA complex is soluble in alkali and is more stable in alkaline than in acid media, but the ligand is rapidly destroyed by the radiation and solvent radiolysis products 12). However, EDTA can apparently be used to complex trace polonium in the separation of radium D-E-F mixtures (129). 

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. 

Potassium iodide is coloured sky-blue when heated in a sealed tube with the vapours of potassium or sodium. The salt is also coloured by cathode rays.41 The decomposition of soln. of the alkali iodides by exposure to radium radiations, and ultra-violet light increases with increasing cone. A. Kailan supposed the radiations decompose the undissociated iodide liberating iodine and hydrogen both in acid and in alkaline soln. Aq. soln. of the alkali iodides are neutral, but, as 0. Loew 42 has shown, the soln. gradually acquires a yellow colour and an alkaline reaction when kept for say 8 to 10 days if air be excluded, the soln. remained colourless for 4 months. A. Houzeau attributed the effect to the presence of traces... 

RADIUM. [CAS 7440-14-41, Chemical element symbol Ra, at. no. 88, at. wt. 226.025, periodic table group 2 (alkaline earths), mp 700VC, bp 1,140°C, density 5 g/cm3 (20°C). Radium metal is white, rapidly oxidized in air, decomposes H O, and evolves heat continuously at the rate of approximately 0.132 calorie per hour per mg when the decomposition products are retained, and the temperature of radium salts remains about 1,5°C above the surrounding environment. Radium is formed by radioactive transformation of uranium, about 3 million parts of uranium being accompanied in nature by 1 part radium. Radium spontaneously generates radon gas at approximately the rate of 100 mmJ per day per gram of radium, at standard conditions, Radium usually is handled as the chloride or bromide, either as solid or in solution. The radioactivity of the material... 

In many of its chemical properties, radium is like the elements magnesium, caldum, strontium and barium, and it is placed in group 2, as is consistent with its 6s26pcls2 electron configuraUon. Its sulfate (Ksp — 4.2 a 10-1 ) is even more insoluble in water than barium sulfate, with which it is conveniently coprecipitated, Like barium and other alkaline earth metals, it forms a soluble chloride (X p = 0,4) and bromide, which can also be obtained as dihydrates, Radium also resembles the other group 2 elements in forming an insoluble carbonate and a very slightly soluble lodate (Xsp = 8.8 x 1(T10). 

The presence of radium in biological materials or environmental samples is generally determined by virtue of its radioactivity. Except in the laboratory where radium compounds have been isolated and determined for a certain purpose, determination of radium compounds in biological and environmental samples is relatively rare. As a Group IIA alkaline earth element, radium is similar in its chemical behavior to other members of that group, especially its nearest neighbor, barium. For example, radium tends to precipitate as the sulfate, which is the basis for its isolation for chemical analysis by coprecipitation with barium sulfate. Furthermore, radium associates with calcium in living systems and accumulates in bone. The determination of radium compounds or specific isotopes is usually accomplished by a separation procedure, followed by quantitative analysis of total radium based on its radioactivity. 

Group 1 elements, beginning with lithium (Li) and running vertically to francium (Fr), are called alkali metals. Group 2 elements, beginning with beryllium (Be) and running vertically to radium (Ra), are called the alkaline earth metals. 

Once again, the periodic table offers clues about which elements could be radioactive naturally. All of the elements in Period 7—like francium in the alkali metals and radium in the alkaline earth metals—are large atoms with many protons. All of the Period 7 elements are radioactive. 

Beryllium, magnesium, calcium, strontium, barium, and radium constitute Group 2 in the Periodic Table. These elements (or simply the Ca, Sr, and Ba triad) are often called alkaline-earth metals. Some important properties of group 2 elements are summarized in Table 12.5.1. 

Alkali metals lithium, sodium, potassium, rubidium, cesium, and francium. Metals such as sodium and potassium (the alkali metals) react violently with water—too violently to conduct experiments. The group 2 metals (also called alkaline earth metals) react less readily and can be used in the laboratory. Alkaline earth metals, including beryllium, magnesium, calcium, strontium, barium, and radium. 

This article sununarizes some of the recent developments in alkaline earth organometalhc chemistry. Several excellent review articles are available for more detailed discussions on the subject areas. It is important to note that radium, the heaviest alkaline earth metal, is radioactive and no organometallic compounds have been reported. 

The second class of alkaline earth metals involves the heavier congeners, although radium, as a radioactive element, is not studied in detail. The significant increase in ionic size and reduction in electronegativity experienced by these metals (Ca (CN 6) 1.14 A, EN = 1.04 Sr (CN 6) 1.27 A, EN = 0.97 ... 

Radium (Ra) 226 Ra (1600y) 1898 P. and M. Curie Alkaline-earth metal similar to Ba... 

The alkaline-earth metals beryllium, magnesium, calcium, strontium, barium, radium. 

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