The Group VI Elements S, Se, Te, Po

Element Electronic structure Melting point (°C) Boiling point (°C) Radius X2 Covalent radius —X— Electro- negativity 

In addition to such divalent species, the elements form compounds in formal oxidation states IV and VI with 4, 5 or 6 bonds tellurium may give an 8-coordinate ion, TeF . Some examples of compounds of Group VI elements and their stereochemistries are listed in Table 15-2. 

The maximum coordination number is not limited to four, nor is the valence limited to two, as in the case of oxygen, since d orbitals may be utilized in bonding. Thus sulfur forms several hexacoordinate compounds, for example, SFfi, and for tellurium six is the characteristic coordination number. 

Gradual changes of properties are evident with increasing size, decreasing electronegativity, etc., such as  

Decreasing thermal stability of the H2X compounds. Thus H2Te is considerably endothermic. 

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All the Group VI elements of the Periodic Table have isotopes with nuclear properties (A 1) which are not very favourable for NMR applications 0 and S have nuclear quadrupole moments and very low natural abundance Se, Te, and Te are gin 1/2 nuclei with low ( Te) or moderate natural abundance Po is radioactive with a half-life of 103 y. The nuclear properties of Po have been examined only by hyperfine structure investigations (A 2) I = 1/2, y = +0.76 yj. Data which are important for NMR investigations are collected in Table 1. The magnetic... 

Group VI (chalcogens) are the elements O, S, Se, Te, and Po. Their outer electron configuration is s2pA. 

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