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The Element Selenium

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Definition of the Selenium Element
Selenium is a solid. It is a non-metallic element, red in powder form, black in vitreous form, and metallic gray in crystalline form, resembling sulfur and tellurium. It is obtained primarily as a by-product of electrolytic Copper refining. It is widely used in rectifiers, as a semiconductor, and in xerography. Its photovoltaic and photoconductive actions make it useful in photocells, photographic exposure meters, and solar cells. The Atomic Number of this element is 34 and the Element Symbol is Se.

The Properties of the Selenium Element
Symbol of Element : Se
Atomic Number : 34
Atomic Mass: 78.96 amu
Melting Point: 217.0 C - 490.15 K
Boiling Point: 684.9 C - 958.05005 K
Number of Protons/Electrons: 34
Number of Neutrons: 45
Crystal Structure: Hexagonal
Density @ 293 K: 4.79 g/cm3
Color: gray, red & black

Origin / Meaning of the name Selenium
The name originates from the Greek Selene, who was the Greek goddess of the moon because the element is chemically found with tellurium (Tellus - the Roman goddess of the earth).

Periodic Table Group and Classification of the of the Selenium Element
Elements can be classified based on their physical states (States of Matter) e.g. gas, solid or liquid. This element is a solid. Selenium is classified as an element in the 'Non-Metals' section which can be located in groups 14,15 and 16 of the Periodic Table. Non-metallic elements exist, at room temperature, in two of the three states of matter: gases (Oxygen, Hydrogen & Nitrogen) and solids (Carbon, Phosphorus, Sulfur and Selenium).

Facts about the Discovery and History of the Selenium Element
Selenium was discovered by Jons Jacob Berzelius in 1817

Occurrence of the Selenium Element
Occurs as selenide in many sulfide ores
Obtained primarily as a by-product of electrolytic copper refining

Abundances of the element in different environments
% in Universe 310-6%
% in Sun N/A
% in Meteorites 0.0013%
% in Earth's Crust 510-6%
% in Oceans 4.510-8%
% in Humans 510-6%

Associated Uses of Selenium
TV cameras
Xerography
Photographic equipment

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