Chemical Elements.com - Selenium (Se)

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Basic Information

Name: Selenium
Symbol: Se
Atomic Number: 34
Atomic Mass: 78.96 amu
Melting Point: 217.0 °C (490.15 K, 422.6 °F)
Boiling Point: 684.9 °C (958.05005 K, 1264.8201 °F)
Number of Protons/Electrons: 34
Number of Neutrons: 45
Classification: Non-metal
Crystal Structure: Hexagonal
Density @ 293 K: 4.79 g/cm³
Color: gray

Atomic Structure

Number of Energy Levels: 4

First Energy Level:

Second Energy Level:

Third Energy Level:

Fourth Energy Level:

Isotopes

Isotope	Half Life
Se-73	7.15 hours
Se-74	Stable
Se-75	119.78 days
Se-76	Stable
Se-77	Stable
Se-78	Stable
Se-79	65000.0 years
Se-80	Stable
Se-82	Stable

Facts

Date of Discovery: 1817
Discoverer: Jons Berzelius
Name Origin: From the Greek word Selênê (Moon)
Uses: photoelectric cells, TV cameras
Obtained From: refining of lead, copper, nickel

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