Barium elemental properties

In general, the chemistry of inorganic lead compounds is similar to that of the alkaline-earth elements. Thus the carbonate, nitrate, and sulfate of lead are isomorphous with the corresponding compounds of calcium, barium, and strontium. In addition, many inorganic lead compounds possess two or more crystalline forms having different properties. For example, the oxides and the sulfide of bivalent lead are frequendy colored as a result of their state of crystallisation. Pure, tetragonal a-PbO is red pure, orthorhombic P PbO is yeUow and crystals of lead sulfide, PbS, have a black, metallic luster. 

Strontium [7440-24-6] Sr, is in Group 2 (IIA) of the Periodic Table, between calcium and barium. These three elements are called alkaline-earth metals because the chemical properties of the oxides fall between the hydroxides of alkaU metals, ie, sodium and potassium, and the oxides of earth metals, ie, magnesium, aluminum, and iron. Strontium was identified in the 1790s (1). The metal was first produced in 1808 in the form of a mercury amalgam. A few grams of the metal was produced in 1860—1861 by electrolysis of strontium chloride [10476-85-4]. 

Barium is a member of the aLkaline-earth group of elements in Group 2 (IIA) of the period table. Calcium [7440-70-2], Ca, strontium [7440-24-6], Sr, and barium form a closely aUied series in which the chemical and physical properties of the elements and thek compounds vary systematically with increa sing size, the ionic and electropositive nature being greatest for barium (see Calcium AND CALCIUM ALLOYS Calcium compounds Strontium and STRONTIUM compounds). As size increases, hydration tendencies of the crystalline salts increase solubiUties of sulfates, nitrates, chlorides, etc, decrease (except duorides) solubiUties of haUdes in ethanol decrease thermal stabiUties of carbonates, nitrates, and peroxides increase and the rates of reaction of the metals with hydrogen increase. 

A waste is toxic under 40 CFR Part 261 if the extract from a sample of the waste exceeds specified limits for any one of eight elements and five pesticides (arsenic, barium, cadmium, chromium, lead, mercury, selenium, silver, endrin, methoxychlor, toxaphene, 2,4-D and 2,4,5-TP Silvex using extraction procedure (EP) toxicity test methods. Note that this narrow definition of toxicity relates to whether a waste is defined as hazardous for regulatory purposes in the context of this chapter, toxicity has a broader meaning because most deep-well-injected wastes have properties that can be toxic to living organisms. 

The material is impact-sensitive when dry and is supplied and stored damp with ethanol. It is used as a saturated solution and it is important to prevent total evaporation, or the slow growth of large crystals which may become dried and shock-sensitive. Lead drains must not be used, to avoid formation of the detonator, lead azide. Exposure to acid conditions may generate explosive hydrazoic acid [1], It has been stated that barium azide is relatively insensitive to impact but highly sensitive to friction [2], Strontium, and particularly calcium azides show much more marked explosive properties than barium azide. The explosive properties appear to be closely associated with the method of formation of the azide [3], Factors which affect the sensitivity of the azide include surface area, solvent used and ageing. Presence of barium metal, sodium or iron ions as impurities increases the sensitivity [4], Though not an endothermic compound (AH°f —22.17 kJ/mol, 0.1 kj/g), it may thermally decompose to barium nitride, rather than to the elements, when a considerable exotherm is produced (98.74 kJ/mol, 0.45 kJ/g of azide) [5]. 

After the Curies, with the assistance of M. G. Bemont, had carried out many laborious fractionations of barium chloride, they found that the most insoluble fractions were the most radioactive. In the course of her experiments Mme. Curie had learned that radioactivity is an atomic property depending solely on the quantity of active element present." For this reason the presence of another active element was suspected, and the radioactive barium chloride was therefore submitted to M. Demarcay for spectroscopic examination. He detected a new line in the ultraviolet region of the spectrum, and certain other lines, all of which were most distinct in the most radioactive preparations, and, as fractionation proceeded, the barium lines became fainter and fainter (23, 28, 52). 

Scheele publishes his famous treatise Concerning Manganese and its Properties, which led to the discovery of three elements manganese, barium, and chlorine. 

As the number of elements increased, so did attempts to organize them into meaningful relationships. Johann Dobereiner (1780-1849) discovered in 1829 that certain elements had atomic masses and properties that fell approximately mid-way between the masses and properties of two other elements. Dobereiner termed a set of three elements a triad. Thus, chlorine, bromine, and iodine form a triad Dobereiner proposed several other triads (lithium-sodium-potassium, calcium-strontium-barium). Dobereiner recognized that there was some sort of relationship between elements, but many elements did not fit in any triad group, and even those triads proposed displayed numerous inconsistencies. 

Curium trifluoride cun be reduced tn Ihc metal hy healing ill 275 C in a beryllia crucible wilh barium vapor. The metal is silvery in color and has the properties of an electropositive element in common wilh the other Actinide elements. 

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). 

Alkhazov et al. (99-101) compared the physicochemical properties and catalytic activities of Group II element molybdates. The calcium, strontium, cadmium, and barium molybdates have a scheelite structure... 

However, other scientists had also attempted to categorise the known elements. In 1817, Johann Dobereiner noticed that the atomic weight (now called atomic mass) of strontium fell midway between the weights of calcium and barium. These were elements which possessed similar chemical properties. They formed a triad of elements. Other triads were also discovered, composed of ... 

Group II consists of the five metals beryllium, magnesium, calcium, strontium and barium, and the radioactive element radium. Magnesium and calcium are generally available for use in school. These metals have the following properties. 

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