Selenium Compound (Solid)

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Selenium is a chemical element with symbol Seand atomic number 34. It is a nonmetal with properties that are intermediate between the elements above and below in the periodic tablesulfurand tellurium, and also has similarities to arsenic. It rarely occurs in its elemental state or as pure ore compounds in the Earth's crust. Selenium is found in metal sulfide ores, where it partially replaces the sulfur. Commercially, selenium is produced as a byproduct in the refining of these ores, most often during production. Minerals that are pure selenide or selenate compounds are known but rare. The chief commercial uses for selenium today are glassmaking and pigments. Selenium is a semiconductor and is used in photocells. Applications in electronics, once important, have been mostly replaced with silicon semiconductor devices. Selenium is still used in a few types of DC power surge protectorsand one type of fluorescent quantum dot.

Phase at STP solid
Melting point 494 K  (221 °C, 430 °F)
Boiling point 958 K (685 °C, 1265 °F)
Density (near r.t.) gray: 4.81 g/cm3
alpha: 4.39 g/cm3
vitreous: 4.28 g/cm3
when liquid (at m.p.) 3.99 g/cm3
Critical point 1766 K, 27.2 MPa

Heat of fusion

gray: 6.69 kJ/mol
Heat of vaporization 95.48 kJ/mol
Molar heat capacity 25.363 J/(mol·K)