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Atomic symbol Se
Atomic number 34
Classification Non-metal
Atomic mass 79.0 amu
Other Information
Date of discovery 1817
Name of discoverer Jöns Berzelius
Name origin From the Greek word Selênê (Moon)
Uses Photoelectric cells, TV cameras
Obtained from Refining of lead, copper, nickel

Selenium(si-LEE-nee-em) is a conductive non-metal. It is primarily useful in electronic devices, especially in light-sensitive devices.


Selenium was discovered by a Swedish chemist named Jöns Jacob Berzelius, in 1817.[1]

Additional Properties

Melting Point: 428.9 °F (220.5 °C or 493.65 K)

Boiling Point: 1265 °F (685 °C or 958 K)

Density: 4.809 grams per cubic centimeter

State of Matter at Room Temperature: Solid[2]

Color: gray[3]


Selenium's electrical resistance is greatly affected by the amount of light shining on it. Bright light causes it to conduct better, while darkness reduces conductivity. This special property has made selenium useful in devices that respond to the intensity of light, such as electric eyes, photo cells, light meters for cameras and copiers. It is also is able to generate energy in direct sunlight. For this reason, it is a vital ingredient of solar cells.[4] Selenium is also useful in converting alternating current to direct current, which is why it is used in rectifiers.



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