34 Se Selenium
Metalloid, mass: 78.96 u, 5 stable isotopes (74, 76, 77, 78, 80), selenium 82 is nearly stable. Abundance rank (earth/space): 59/29Click image to magnify. Ultrapure black, amorphous selenium, 3 - 4 grams. Original size in cm: 2
Selenium is a metalloid, which has more nonmetallic than metallic properties. Chemically it resembles sulfur, but is less reactive than this. Nonetheless it very rarely occurs in nature in its pure form. Every life form on earth needs selenium in small amounts for different proteins and amino acids. However, if the dose is too high, it quickly becomes poisonous. Hydrogen selenide and many other selenium compounds smell terrible, worse than the according sulfur compounds.

Small pieces of grey, metallic selenium, the most stable allotrope of this element, on the black selenium.
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Page last changed on February 27. 2010
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