Polonium coefficient

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... 

Frey, G., P.K. Hopke and J. Stukel, Effects of Trace Gases and Water Vapor on the Diffusion Coefficient of Polonium-218, Science 211 480-481 (1981). 

Measuring Polonium-218 Diffusion-Coefficient Spectra Using Multiple Wire Screens... 

Frey, G., Hopke, P.K. Stukel, J.J. (1981) Effect of trace gases and water vapour on the diffusion coefficient of polonium-218. Science, 211, 480-1. 

The trend toward greater metallic character of the elements is complete at polonium, which has two allotropes, both with typically metallic structures a cubic, converting at 36°C to /3 rhombohedral (mp 254°C). Each of these has resistivity typical of a true metal with a positive temperature coefficient. 

G. Jia, G. Torri, M. Petruzzi, Distribution coefficients of polonium between 5% TOPO in toluene and aqueous hydrochloric and nitric acids. Appl. Radiat. Isotopes, 2004, 61, 279. 

The trend towards greater metallic character in the elements is complete at polonium. Whereas sulfur is a true insulator (specific resistivity in fiQ-cm = 2 x 1023), selenium (2X1011) and tellurium (2 x10s) are intermediate in their electrical conductivities, and the temperature coefficient of resistivity in all three cases is negative, which is usually considered characteristic of non-metals. Polonium in each of its two allotropes has a resistivity typical of true metals ( 43 juQ-cm) and a positive temperature coefficient. The low-temperature allotrope, which is stable up to about 100°, has a cubic structure, and the high temperature form is rhombohedral. In both forms the coordination number is six. 

Marty B, LeCloarec MF (1992) Hehnm-3 and CO2 flnxes from subaerial volcanoes estimated from Polonium-210 emissions. J Volcanol Geotherm Res 53 67-72 Marly B, Lussiez P (1993) Constraints on rare gas partition coefficients from analysis of olivine glass from a picritic mid-ocean ridge basalt. Chem Geol 106 1-7... 

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