Periodic Table - Selenium - 34th

      selenium

Selenium thirty-fourth element of the Periodic Table

Selenium is a chemical element belonging to group or family 6A of the periodic classification or family of calcogens, has atomic number 34, atomic mass 78.96 g mol-1, melting point 220 ° C and boiling point 685 ° C. The coloration of the element is directly related to its allotropic forms, being the most stable, the hexagonal crystalline that has a metallic gray color, the monoclinic form has a red color and the amorphous selenium has a dark red color tending to black.
It was discovered by JJ Berzélius in the year 1817, driven by Martin Klaprot's claim that the residual coloring of a by-product of sulfuric acid manufacture was tellurium, but Berzélius not satisfied with the statements submitted the analysis to the conclusion. that the waste was a new chemical element. Selenium was discovered, named after being confused with tellurium from the Latin "Tellus" meaning earth goddess, Berzelius decided that the new element he discovered would be called Selenium from the Greek "Selene" which means goddess moon.
Selenium is an element that has characteristics very similar to those of sulfur and tellurium, in its compounds form selenides, selenites and selenates, and also the selenium hydride gas SeH2 (poison), since most selenium compounds have toxic characteristics. .
Amorphous Selenium:
It is obtained as a byproduct from waste from the electrolytic purification of noble metals in industrial scope and is also found in Brazil nuts, which is one of the sources of the element for living beings. Selenium in adequate amounts is part of human nutrition and we find it in meat and vegetables mainly.
The element is used in the glass manufacturing process, as a red color inks, in glass commonly as bleach, in its metallic form in the manufacture of photovoltaic cells due to its property of transforming light energy into electrical energy and as a catalyst in chemical reactions. .
Selenium in Biochemistry:
It is important to stress that selenium, although toxic, plays a fundamental role in maintaining the various life forms, and is indispensable because it forms a class of important proteins called selenoproteins, some of which are listed below as being the most important and responsible for the processes. metabolic effects of the organism of living beings:
     Selenoprotein P
     Selenoprotein W
     Selenophosphate synthetase
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