Osmium

Osmium, ₇₆Os
Osmium
Pronunciation	/ˈɒzmiəm/ (OZ-mee-əm)
Appearance	silvery, blue cast
Standard atomic weight Ar°(Os)
	190.23±0.03; 190.23±0.03 (abridged);
Osmium in the periodic table
	rhenium ← osmium → iridium
Atomic number (Z)	76
Group	group 8
Period	period 6
Block	d-block
Electron configuration	[Xe] 4f14 5d6 6s2
Electrons per shell	2, 8, 18, 32, 14, 2
Physical properties
Phase at STP	solid
Melting point	3306 K (3033 °C, 5491 °F)
Boiling point	5281 K (5008 °C, 9046 °F)
Density (at 20° C)	22.587 g/cm3
when liquid (at m.p.)	20 g/cm3
Heat of fusion	31 kJ/mol
Heat of vaporization	378 kJ/mol
Molar heat capacity	24.7 J/(mol·K)
Atomic properties
Oxidation states	common: +4; −4,? −2, −1,? 0,? +1, +2, +3, +5, +6, +7, +8
Electronegativity	Pauling scale: 2.2
Ionization energies	1st: 840 kJ/mol ; 2nd: 1600 kJ/mol ; ;
Atomic radius	empirical: 135 pm
Covalent radius	144±4 pm
	Spectral lines of osmium
Other properties
Natural occurrence	primordial
Crystal structure	hexagonal close-packed (hcp) (hP2)
Lattice constants	a = 273.42 pm; c = 431.99 pm (at 20 °C)
Thermal expansion	4.99×10−6/K (at 20 °C)
Thermal conductivity	87.6 W/(m⋅K)
Electrical resistivity	81.2 nΩ⋅m (at 0 °C)
Magnetic ordering	paramagnetic
Molar magnetic susceptibility	11×10−6 cm3/mol
Shear modulus	222 GPa
Bulk modulus	462 GPa
Speed of sound thin rod	4940 m/s (at 20 °C)
Poisson ratio	0.25
Mohs hardness	7.0
Vickers hardness	4137 MPa
Brinell hardness	3920 MPa
CAS Number	7440-04-2
History
Discovery and first isolation	Smithson Tennant (1803)
Isotopes of osmium v; e;
	Category: Osmium; view; talk; edit; \| references

Osmium (from Ancient Greek ὀσμή (osmḗ) 'smell') is a chemical element; it has symbol Os and atomic number 76. It is a hard, brittle, bluish-white transition metal in the platinum group that is found as a trace element in alloys, mostly in platinum ores. Osmium is the densest naturally occurring element. When experimentally measured using X-ray crystallography, it has a density of 22.59 g/cm³.^[11] Manufacturers use its alloys with platinum, iridium, and other platinum-group metals to make fountain pen nib tipping, electrical contacts, and in other applications that require extreme durability and hardness.^[12]

Osmium is among the rarest elements in the Earth's crust, making up only 50 parts per trillion (ppt).^[13]^[14]

^ "Standard Atomic Weights: Osmium". CIAAW. 1991.
^ 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. (May 4, 2022). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
^ Rumble, John R.; Bruno, Thomas J.; Doa, Maria J. (2022). "Section 4: Properties of the Elements and Inorganic Compounds". CRC Handbook of Chemistry and Physics: A Ready Reference Book of Chemical and Physical Data (103rd ed.). Boca Raton, FL: CRC Press. p. 40. ISBN 978-1-032-12171-0.
^ Rumble, John R.; Bruno, Thomas J.; Doa, Maria J. (2022). "Section 4: Properties of the Elements and Inorganic Compounds". CRC Handbook of Chemistry and Physics: A Ready Reference Book of Chemical and Physical Data (103rd ed.). Boca Raton, FL: CRC Press. p. 40. ISBN 978-1-032-12171-0.
^ Rumble, John R.; Bruno, Thomas J.; Doa, Maria J. (2022). "Section 4: Properties of the Elements and Inorganic Compounds". CRC Handbook of Chemistry and Physics: A Ready Reference Book of Chemical and Physical Data (103rd ed.). Boca Raton, FL: CRC Press. p. 40. ISBN 978-1-032-12171-0.
^ ^a ^b ^c ^d ^e ^f ^g ^h Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. 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.
^ ^a ^b Haynes 2011, p. 4.134.
^ 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.
^ Peters, Stefan T.M.; Münker, Carsten; Becker, Harry; Schulz, Toni (April 2014). "Alpha-decay of ¹⁸⁴Os revealed by radiogenic ¹⁸⁰W in meteorites: Half life determination and viability as geochronometer". Earth and Planetary Science Letters. 391: 69–76. doi:10.1016/j.epsl.2014.01.030.
^ Cite error: The named reference Arblaster1995 was invoked but never defined (see the help page).
^ Haynes 2011, p. 4.25.
^ Fleischer, Michael (1953). "Recent estimates of the abundances of the elements in the Earth's crust" (PDF). U.S. Geological Survey. Archived (PDF) from the original on October 23, 2022. Retrieved May 10, 2018.
^ "Reading: Abundance of Elements in Earth's Crust | Geology". courses.lumenlearning.com. Archived from the original on May 17, 2022. Retrieved May 10, 2018.

Cite error: There are <ref group=lower-alpha> tags or {{efn}} templates on this page, but the references will not show without a {{reflist|group=lower-alpha}} template or {{notelist}} template (see the help page).

[1] "Standard Atomic Weights: Osmium". CIAAW. 1991.

[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. (May 4, 2022). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.

[3] Rumble, John R.; Bruno, Thomas J.; Doa, Maria J. (2022). "Section 4: Properties of the Elements and Inorganic Compounds". CRC Handbook of Chemistry and Physics: A Ready Reference Book of Chemical and Physical Data (103rd ed.). Boca Raton, FL: CRC Press. p. 40. ISBN 978-1-032-12171-0.

[4] Rumble, John R.; Bruno, Thomas J.; Doa, Maria J. (2022). "Section 4: Properties of the Elements and Inorganic Compounds". CRC Handbook of Chemistry and Physics: A Ready Reference Book of Chemical and Physical Data (103rd ed.). Boca Raton, FL: CRC Press. p. 40. ISBN 978-1-032-12171-0.

[5] Rumble, John R.; Bruno, Thomas J.; Doa, Maria J. (2022). "Section 4: Properties of the Elements and Inorganic Compounds". CRC Handbook of Chemistry and Physics: A Ready Reference Book of Chemical and Physical Data (103rd ed.). Boca Raton, FL: CRC Press. p. 40. ISBN 978-1-032-12171-0.

[GE28-6] ^ ^a ^b ^c ^d ^e ^f ^g ^h Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.

[Arblaster_2018-7] Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.

[FOOTNOTEHaynes20114.134-9] Haynes 2011, p. 4.134.

[NUBASE2020-10] 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.

[184Os-11] Peters, Stefan T.M.; Münker, Carsten; Becker, Harry; Schulz, Toni (April 2014). "Alpha-decay of ¹⁸⁴Os revealed by radiogenic ¹⁸⁰W in meteorites: Half life determination and viability as geochronometer". Earth and Planetary Science Letters. 391: 69–76. doi:10.1016/j.epsl.2014.01.030.

[Arblaster1995-12] Cite error: The named reference Arblaster1995 was invoked but never defined (see the help page).

[FOOTNOTEHaynes20114.25-13] Haynes 2011, p. 4.25.

[14] Fleischer, Michael (1953). "Recent estimates of the abundances of the elements in the Earth's crust" (PDF). U.S. Geological Survey. Archived (PDF) from the original on October 23, 2022. Retrieved May 10, 2018.

[15] "Reading: Abundance of Elements in Earth's Crust | Geology". courses.lumenlearning.com. Archived from the original on May 17, 2022. Retrieved May 10, 2018.

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