The periodic table/Selenium
Subject classification: this is a chemistry resource. |
Completion status: this resource is considered to be ready for use. |
Type classification: this is an article resource. |
Educational level: this is a research resource. |
Discovery
editSelenium was discovered by Jöns Jacob Berzelius in Stockholm, Sweden, in 1817. The name is derived from 'selene', the Greek name for the Moon.
Quick Facts
editName: Selenium Symbol: Se Mass: 78.963 Atomic Number: 34 Electron Configuration: [Ar] 3d10 4s2 4p4 |
Classification: non-metal CAS Number: 7782-49-2 Appearance: Either as a silvery semi-metal or as a red powder Discovery in: 1817 Key Isotopes: 80Se Allotropes: Red Se, Black Se, Grey Se |
Uses
editSelenium has both a photovoltaic action (converts light to electricity) and a photoconductive action (electrical resistance decreases with increased illumination). Selenium is therefore useful in photocells and solar cells. It can also convert a.c. electricity to d.c. electricity, so is extensively used in rectifiers. It is used by the glass industry, and to make stainless steel. It is also used in photocopiers.
Selenium is an essential trace element for some species, including humans, and our bodies contain about 14 milligrams. However, it is toxic in excess. It is carcinogenic and teratogenic.
Atomic Data
editAtomic radius: 1.900 Å Covalent radius: 1.18 Å Electronegativity: 2.550 Electron affinity: 194.997 kJ mol-1 |
Ionisation energies First: 940.961 kJ mol-1 Second: 2044.523 kJ mol-1 Third: 2973.714 kJ mol-1 Fourth: 4143.559 kJ mol-1 Fifth: 6589.943 kJ mol-1 Sixth: 7882.846 kJ mol-1 Seventh: 14993.809 kJ mol-1 |
Supply Risk
editScarcity factor: 4.5 (low risk)
Crustal abundance: 0.13 ppm Reserve base distribution: 23.3% Production concentration: 34.8% |
Top 3 countries for mining:
|
Top 3 countries for production:
|
Oxidation States and Isotopes
editCommon oxidation states: 6, 4, -2
Isotopes
Isotope | Atomic mass | Abundance (%) | Half life | Mode of decay |
---|---|---|---|---|
74Se | 73.922 | 0.89 | > 5.5 x 1018 years | EC-EC |
76Se | 75.919 | 9.37 | ||
77Se | 76.92 | 7.63 | ||
78Se | 77.917 | 23.77 | ||
80Se | 79.917 | 49.61 | ||
82Se | 81.917 | 8.73 | > 9.5 x 1019 years | β-β- |
Pressure and Temperature Data
editMolar heat capacity: 25.363 J mol-1 K-1