Selenium is located on the fourth period and the sixteenth group in the periodic table of elements. It is a grayish metallic solid with a melting point of 221 degrees Celsius. Selenium can be considered a member of the metalloids. It can form up to 2 bonds. Selenium was identified in 1817 by Jons Jacob Berzelius. Its compounds are even stinkier than those of Sulfur. And in high concentrations, it can be toxic. It has 2 allotropes, black Selenium and red Selenium. Black amorphous Selenium exists in a vitreous form, and red Selenium exists as a powder. Crystalline Selenium is also red.
Selenium is an essential part of the human body, it is useful as a pigment, and in the photovoltaic industry.