Selenium information

Selenium, ₃₄Se
Selenium
Pronunciation	/sɪˈliːniəm/ (sə-LEE-nee-əm)
Appearance	grey metallic-looking, red, and vitreous black (not pictured) allotropes
Standard atomic weight Ar°(Se)
	78.971±0.008; 78.971±0.008 (abridged);
Selenium in the periodic table
	arsenic ← selenium → bromine
Atomic number (Z)	34
Group	group 16 (chalcogens)
Period	period 4
Block	p-block
Electron configuration	[Ar] 3d10 4s2 4p4
Electrons per shell	2, 8, 18, 6
Physical properties
Phase at STP	solid
Melting point	494 K (221 °C, 430 °F)
Boiling point	958 K (685 °C, 1265 °F)
Density (near r.t.)	gray: 4.81 g/cm3 ; alpha: 4.39 g/cm3 ; vitreous: 4.28 g/cm3
when liquid (at m.p.)	3.99 g/cm3
Critical point	1766 K, 27.2 MPa
Heat of fusion	gray: 6.69 kJ/mol
Heat of vaporization	95.48 kJ/mol
Molar heat capacity	25.363 J/(mol·K)
Atomic properties
Oxidation states	−2, −1, 0, +1, +2, +3, +4, +5, +6 (a strongly acidic oxide)
Electronegativity	Pauling scale: 2.55
Ionization energies	1st: 941.0 kJ/mol ; 2nd: 2045 kJ/mol ; 3rd: 2973.7 kJ/mol ; ;
Atomic radius	empirical: 120 pm
Covalent radius	120±4 pm
Van der Waals radius	190 pm
	Spectral lines of selenium
Other properties
Natural occurrence	primordial
Crystal structure	grey: hexagonal (hP3)
Lattice constants	a = 436.46 pm; c = 495.77 pm (at 20 °C)
Thermal expansion	amorphous: 37 µm/(m⋅K) (at 25 °C)
Thermal conductivity	amorphous: 0.519 W/(m⋅K)
Magnetic ordering	diamagnetic
Molar magnetic susceptibility	−25.0×10−6 cm3/mol (298 K)
Young's modulus	10 GPa
Shear modulus	3.7 GPa
Bulk modulus	8.3 GPa
Speed of sound thin rod	3350 m/s (at 20 °C)
Poisson ratio	0.33
Mohs hardness	2.0
Brinell hardness	736 MPa
CAS Number	7782-49-2
History
Naming	after Selene, Greek goddess of the moon
Discovery and first isolation	Jöns Jakob Berzelius and Johann Gottlieb Gahn (1817)
Isotopes of selenium v; e;
γ	–
γ	–
	Category: Selenium; view; talk; edit; \| references

Selenium is a chemical element; it has the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, and also has similarities to arsenic.^[9] It seldom occurs in its elemental state or as pure ore compounds in Earth's crust. Selenium (from Ancient Greek σελήνη (selḗnē) 'moon') was discovered in 1817 by Jöns Jacob Berzelius, who noted the similarity of the new element to the previously discovered tellurium (named for the Earth).

Selenium is found in metal sulfide ores, where it partially replaces the sulfur. Commercially, selenium is produced as a byproduct in the refining of these ores, most often during production. Minerals that are pure selenide or selenate compounds are known but rare. The chief commercial uses for selenium today are glassmaking and pigments. Selenium is a semiconductor and is used in photocells. Applications in electronics, once important, have been mostly replaced with silicon semiconductor devices. Selenium is still used in a few types of DC power surge protectors and one type of fluorescent quantum dot.

Although trace amounts of selenium are necessary for cellular function in many animals, including humans, both elemental selenium and (especially) selenium salts are toxic in even small doses, causing selenosis.^[10] Selenium is listed as an ingredient in many multivitamins and other dietary supplements, as well as in infant formula, and is a component of the antioxidant enzymes glutathione peroxidase and thioredoxin reductase (which indirectly reduce certain oxidized molecules in animals and some plants) as well as in three deiodinase enzymes. Selenium requirements in plants differ by species, with some plants requiring relatively large amounts and others apparently not requiring any.^[11]

^ "Standard Atomic Weights: Selenium". CIAAW. 2013.
^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
^ A Se(0) atom has been identified using DFT in [ReOSe(2-pySe)₃]; see Cargnelutti, Roberta; Lang, Ernesto S.; Piquini, Paulo; Abram, Ulrich (2014). "Synthesis and structure of [ReOSe(2-Se-py)3]: A rhenium(V) complex with selenium(0) as a ligand". Inorganic Chemistry Communications. 45: 48–50. doi:10.1016/j.inoche.2014.04.003. ISSN 1387-7003.
^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
^ Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.
^ Magnetic susceptibility of the elements and inorganic compounds, in Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
^ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
^ Cite error: The named reference ge was invoked but never defined (see the help page).
^ Fernández-Bautista, Tamara; Gómez-Gómez, Beatriz; Palacín-García, Roberto; Gracia-Lor, Emma; Pérez-Corona, Teresa; Madrid, Yolanda (2022-01-15). "Analysis of Se and Hg biomolecules distribution and Se speciation in poorly studied protein fractions of muscle tissues of highly consumed fishes by SEC-UV-ICP-MS and HPLC-ESI-MS/MS". Talanta. 237: 122922. doi:10.1016/j.talanta.2021.122922. ISSN 0039-9140. PMID 34736659. S2CID 243761320.
^ Ruyle, George. "Poisonous Plants on Arizona Rangelands" (PDF). The University of Arizona. Archived from the original (PDF) on 15 July 2004. Retrieved 5 January 2009.

[1] "Standard Atomic Weights: Selenium". CIAAW. 2013.

[CIAAW2021-2] Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.

[3] A Se(0) atom has been identified using DFT in [ReOSe(2-pySe)₃]; see Cargnelutti, Roberta; Lang, Ernesto S.; Piquini, Paulo; Abram, Ulrich (2014). "Synthesis and structure of [ReOSe(2-Se-py)3]: A rhenium(V) complex with selenium(0) as a ligand". Inorganic Chemistry Communications. 45: 48–50. doi:10.1016/j.inoche.2014.04.003. ISSN 1387-7003.

[4] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.

[Arblaster_2018-5] Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.

[6] Magnetic susceptibility of the elements and inorganic compounds, in Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.

[7] Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.

[NUBASE2020-8] Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.

[ge-9] Cite error: The named reference ge was invoked but never defined (see the help page).

[10] Fernández-Bautista, Tamara; Gómez-Gómez, Beatriz; Palacín-García, Roberto; Gracia-Lor, Emma; Pérez-Corona, Teresa; Madrid, Yolanda (2022-01-15). "Analysis of Se and Hg biomolecules distribution and Se speciation in poorly studied protein fractions of muscle tissues of highly consumed fishes by SEC-UV-ICP-MS and HPLC-ESI-MS/MS". Talanta. 237: 122922. doi:10.1016/j.talanta.2021.122922. ISSN 0039-9140. PMID 34736659. S2CID 243761320.

[Ruyle-11] Ruyle, George. "Poisonous Plants on Arizona Rangelands" (PDF). The University of Arizona. Archived from the original (PDF) on 15 July 2004. Retrieved 5 January 2009.

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