Polonium sulfur

Eighteen isotopes of sulfur, 17 of selenium, 21 of tellurium, and 27 of polonium have been registered of these, 4 sulfur, 6 selenium, and 8 tellurium isotopes are stable, while there is no stable isotope of polonium. None of the naturally occurring isotopes of Se is radioactive its radioisotopes are by-products of the nuclear reactor and neutron activation technology. The naturally occurring, stable isotopes of S, Se, and Te are included in Table 1.2. 

Basic physical properties of sulfur, selenium, and tellurium are indicated in Table 1.3. Downward the sulfur sub-group, the metallic character increases from sulfur to polonium, so that whereas there exist various non-metallic allotropic states of elementary sulfur, only one allotropic form of selenium is (semi)metallic, and the (semi)metallic form of tellurium is the most common for this element. Polonium is a typical metal. Physically, this trend is reflected in the electrical properties of the elements oxygen and sulfur are insulators, selenium and tellurium behave as semiconductors, and polonium is a typical metallic conductor. The temperature coefficient of resistivity for S, Se, and Te is negative, which is usually considered... 

Liquid tellurium boils at 990 °C to a golden yellow vapor, with density that corresponds to the molecular formula T 2- Likewise, in polonium vapor only P02 species are present. Clearly, the decreasing complexity of the solid state of the three elements Se, Te, and Po, as compared to sulfur, is reflected in the vapor state. 

Within the sulfur sub-group, there are two main types of oxides, the dioxides X 02 (X = S, Se, Te, Po) and the trioxides X Os (X = S, Se, Te). In addition, sulfur also forms disulfur monoxide, S2O. Transient XO species are known in the gaseous phase for S, Se, and Te. Polonium forms a black monoxide PoO. 

Although the sulfur-gold bond has been most investigated, the Group 16 elements selenium and tellurium have also attracted attention and are discussed in detail here (polonium has not received attention due to its radioactivity). 

Selenium, tellurium, and polonium have not been as well studied as oxygen and sulfur, but they are known to form several long chains of atoms. Different lengths and arrangements of the chains cause differences in the way the elements look and react. 

The chemistry of sulfur is a broad area that includes such chemicals as sulfuric acid (the compound prepared in the largest quantity) as well as unusual compounds containing nitrogen, phosphorus, and halogens. Although there is an extensive chemistry of selenium and tellurium, much of it follows logically from the chemistry of sulfur if allowance is made for the more metallic character of the heavier elements. All isotopes of polonium are radioactive, and compounds of the element are not items of commerce or great use. Therefore, the chemistry of sulfur will be presented in more detail. 

All five elements in the oxygen group have six electrons in their outer orbits. They are all oxidizers (they accept electrons), but they are not all alike. They range from a nonmetal gas (oxygen) to a nonmetal solid (sulfur) to a nonmetallic semiconductor (selenium) to a semimetal (tellurium) and finally to a radioactive metal (polonium). 

R. C. Brasted, Comprehensive Inorganic Chemistry, Vol. 8, Sulfur, Selenium, Tellurium, Polonium, and Oyygen, D. Van Nostrand Co., Inc., Princeton, N.J.,... 

The heaviest elements in every group of the Periodic Table have a special interest because of the marked change in properties which occurs in passing down a group thus, in the heaviest member, the maximum group valency is achieved with difficulty, if at all. In the sulfur family (group 6B), of which polonium is the heaviest member, there is the added interest of a gradation from nonmetallic to metallic properties. 

Unlike its lower homologues, sulfur, selenium, and tellurium, polonium has no long-lived or stable isotopes. It has, in fact, one of the most unstable nuclei of naturally occurring elements, the only readily accessible isotope being that of mass 210 this decays by alpha emission with a half-life of 138.4 days and occurs in nature as the penultimate member of the radium decay series, the last three stages being... 

For the chemical separation, the irradiated bismuth is dissolved in acid, tellurium carrier is added, and metallic polonium and bismuth are precipitated from solution with stannous chloride (96, 117). The metals are dissolved in acid and the tellurium reprecipitated with sulfur dioxide (76), leaving polonium in solution in the bipositive state. 

The physical properties of the metal (Table II) resemble those of thallium, lead and bismuth, its neighbors in the Periodic Table, rather than those of tellurium, its lower homologue. The low melting and boiling points are particularly noteworthy an attempted study of the Hall effect in polonium metal has also been reported (90). In chemical properties the metal is very similar to tellurium, the most striking resemblance being in its reactions with concentrated sulfuric acid (or sulfur trioxide) and with concentrated selenic acid. The products are the bright red solids, PoSOs and... 

A white solid, possibly polonium tetrafluoride, is obtained by treating polonium hydroxide or tetrachloride with dilute aqueous hydrofluoric acid treatment of this solid, in suspension in dilute hydrofluoric acid, with sulfur dioxide yields a bluish grey product (possibly PoF2) which rapidly reverts to the original white solid on standing, presumably owing to radio-lytic oxidation 12). The solubility of polonium(IV) in aqueous hydrofluoric acid increases rapidly with acid concentration, indicating complex ion formation (/ft), p. 48). 

Bipositive polonium in hydrochloric acid solution (pink) is oxidized to polonium(lV) by hydrogen peroxide, by hypochlorous acid or by the radiolysis products of the alpha bombardment of the solvent. Solutions of polonium(II) in acid are obtained by the reduction of polonium(lV) with sulfur dioxide or hydrazine in the cold, or with arsenious oxide on warming. Polonium (IV) is not reduced in hydrochloric acid by either hydroxylamine or oxalic acid, even on boiling 6). 

The white basic sulfate, 2Po02-S03, results when polonium(IV) hydroxide or chloride is treated with 0.02 N-0.25 N sulfuric acid. Like the selenate, it is yellow above 250°C and decomposes to the dioxide at 550°C. Solubility studies indicate that it is metastable in contact with 0.1 N-0.5 N sulfuric acid (10). 

Suspensions of the disulfate in N-2 N sulfuric acid dissolve on boiling with hydroxylamine to give a pink solution, characteristic of polonium(II), but the disulfate hydrate is reprecipitated on cooling, even in the presence of an excess of hydroxylamine (10), in accord with earlier trace level... 

Sulfur, selenium, tellurium and polonium constitute the heavier elements of group VIB of the periodic table and are sometimes referred to as the chalcogens, chalcogenins, chalcogenides or chalconides. Developments in the understanding and interest in the chemistry of these elements have been reviewed at appropriate intervals during the past 20 years.1-8... 

Sulfur, Selenium, Tellurium and Polonium Table 1 Compounds of Group VI Elements and their Stereochemistries... 

Although there are similarities between the chemistry of the chalcogenide elements, the properties of selenium and tellurium clearly lie between those of non-metallic sulfur and metallic polonium. The enhancement in metallic character as the group is descended is illustrated in the emergence of cationic properties by polonium, and marginally by tellurium, which are reflected in the ionic lattices of polonium(IV) oxide and tellurium(IV) oxide and the formation of salts with strong acids. 

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