Group 16 elements polonium

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... 

In the fourth group, carbon and silicon are both non-metallic, while germanium has a very small electrical conductivity. It is only with white tin and lead that the electrical conductivity approaches the normal values for true metals. In the fifth group, arsenic and antimony are just on the limit between metallic and non-metallic properties, while of the elements of the sixth group, only polonium might be considered to have real metallic properties. The halogens, in the seventh group, show no trace of metallic properties. 

The product in this case is sodium aluminate, a compound that contains the aluminate ion, [Al(OH)4]. Because aluminum oxide reacts with both acids and bases, it is classified as amphoteric. Other main-group elements that form amphoteric oxides are shown in Fig. J.3. As you can see, these elements lie in a diagonal band across the table from beryllium to polonium. The acidic, amphoteric, or basic character of the oxides of the d-block metals depends on their oxidation state (see Chapter 16). 

All of the chalcogens form chalcogenide 2 anions such as oxides, sulfides, selenides, and tellurides. Selenium is used in photocopiers, it makes the electrostatic charge on the paper that directs where the ink sticks. Polonium is the most unique element in this period since it is a metal. Keep reading to find out the important properties of oxygen and sulfur, two very important chalcogen group elements. 

Elements at the right of the p block have characteristically high electron affinities they tend to gain electrons to complete closed shells. Except for the metalloids tellurium and polonium, the members of Groups 16/VI and 17/VII are nonmetals (Fig. 1.62). They typically form molecular compounds with one another. They react with metals to form the anions in ionic compounds, and hence many of the minerals that surround us, such as limestone and granite, contain anions formed from non-metals, such as S2-, CO,2-, and S042-. Much of the metals industry is concerned with the problem of extracting metals from their combinations with nonmetals. 

Polonium, completing the elements of Group 16, is radioactive and one of the rarest naturally occurring elements (about 3 x 10 " % of the Earth s crust). The main natural source of polonium is uranium ores, which contain about lO g of Po per ton. The isotope 210-Po, occurring in uranium (and also thorium) minerals as an intermediate in the radioactive decay series, was discovered by M. S. Curie in 1898. 

The trend toward more metallic character of the elements in Group 16 is complete at polonium, which has two allotropes, both with typically metallic structures a-cubic, which converts at 36 °C to P-rhombohedral (m.p. 254 "C). 

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). 

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). 

Polonium is more metallic in its properties than the elements above it in group 16. It is the only element in group 16 that is naturally radioactive. It is in a position on the periodic table of elements where it can be a metal, metalloid, or nonmetal. It is more often considered a metal because of its electrical conductivity decreases with an increase in temperature. 

Element 116 was also directly produced by bombarding atoms of curiiim-248 with ions of high-energy calcium-48 ions. At the bottom of group 6 (VIA) on the periodic table, Uuh is presumed to have some of the properties and characteristics of its homologues polonium and tellurium, located just above it in this group. 

Table Group VIIB (the halogens), is the earth s rarest naturally occurring element. All its isotopes are radioactive (Table I), hence the Greek name aoTaTCoC, meaning unstable 44, 45). The possibility of their existence was predicted from the -decay of polonium (55). Its three naturally occurring isotopes, At, At, and At, are the extremely short-lived natural daughters of AcA (77), RaA (76,173), and AcK (72), respectively.

Polonium resembles tellurium, the element above it in the same Group, in chemical behavior. 

Elements bordering the staircase (boron, silicon, germanium, arsenic, antimony, tellurium, polonium, and astatine) are called metalloids because they have properties between those of metals and nonmetals. Chemists debate the membership of certain elements (especially polonium and astatine) within the metalloids, but the list here reflects an inclusive view. You can find these elements in Groups lllA, IVA, VA, VIA, and VllA. 

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. 

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. 

The group VIB cyanides, thiocyanates and selenocyanates and their complexes with species such as thiourea have been described.1,45 For example, the tellurium dithiocyanate complex has been prepared45 by treatment of tellurium dichloride or tellurium dibromide with ammonium thiocyanate. It seems that little information exists on the preparation of tellurocyanates and there is a sparsity of data on polonium derivatives. Indeed, the only known cyanide of polonium is probably a salt of the quadrivalent element.1... 

The oxo acid complexes of the group VIB elements are largely restricted to those of tellurium and polonium and the information on these types of materials has not changed significantly in recent years.4... 

For Oxygon, see this Series, Vol. VII., Part I. for Polonium, see Vol. III., Part I. a The general characteristics of the elements of Subdivision A are dealt with in this Series, Vol. VII., Part III., Chapter I. Those of the elements of Group VI. considered as a wholo are dealt with in VoCjVTI., Part I., Chapter I. 

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