Selenium is the 34th element, a nonmetal, it has 2 allotropes - a purple/gray one and a red one, the purple/gray one being the most stable. Its chemical symbol is Se.
It is rarely found in nature but occurs as a compound in minerals.
The purple/gray allotrope is a semi conductor and it has an unusual property - it is a better conductor in the light than in the dark.
At number 34, Selenium has 34 electrons. This means that it has 2 spaces in its outer shell - just like oxygen and sulphur. Selenium forms similar compounds to sulphur - SeO2 and H2Se for example
Although it is extremely toxic in large doses, it is present at trace levels in humans and thought to be essential for the correct functioning of the body. We get our Selenium from eating plants and animals that contain Selenium. Brazil nuts have the highest concentration of any food. It is also contained in crab and lobster meat.
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