Osmium (Os)
transition-metalSolid
Peso atomico standard
190,23 uConfigurazione elettronica
[Xe] 6s2 4f14 5d6Punto di fusione
3032,85 °CPunto di ebollizione
5011,85 °CDensità
2,25872e+4 kg/m³Stati di ossidazione
−4, −2, −1, 0, +1, +2, +3, +4, +5, +6, +7, +8Elettronegatività (Pauling)
2,2Energia di ionizzazione (1ª)
8,43823 eVAnno della scoperta
1803Raggio atomico
130 pmDettagli
Osmium is a very dense, hard, blue-white platinum-group metal. It is chemically noble in compact metallic form but is notable for forming volatile and highly toxic osmium tetroxide. Natural osmium occurs with other platinum-group elements in ultramafic ores and placer deposits, chiefly as alloys and sulfide-bearing mineral assemblages. Its rarity, difficult fabrication, and toxicity of some compounds limit its use despite unusual physical and chemical properties.
The metal is lustrous, bluish white, extremely hard, and brittle even at high temperatures. It has the highest melting point and the lowest vapor pressure of the platinum group. The metal is very difficult to fabricate, but the powdered or spongy metal slowly gives off osmium tetroxide, which as a powerful oxidizing agent and has a strong smell. The tetroxide is highly toxic, and boils at 130°C.
Density measurements show osmium to be a little more dense than iridium, and osmium is often cited as the heavier element. However, calculations of the density from the space lattice, which may be more reliable than these measurements, give a density of 22.65 for iridium compared to 22.61 for osmium. According to IUPAC, because of this apparent contradiction, no decision has been made as to which is heavier.
The name derives from the Greek osme for "smell" because of the sharp odor of its volatile oxide. Both osmium and iridium were discovered simultaneously in a crude platinum ore by the English chemist Smithson Tennant in 1803.
Osmium and iridium were discovered at the same time by the British chemist Smithson Tennant in 1803. Osmium and iridium were identified in the black residue remaining after dissolving platinum ore with aqua regia, a mixture of 25% nitric acid (HNO3) and 75% hydrochloric acid (HCl). Today, osmium is primarily recovered during the processing of platinum and nickel ores.
Discovered in 1803 by Tennant in the residue left when crude platinum is dissolved by aqua regia.
Pure osmium is a lustrous bluish white to blue-gray metal. It is extremely dense and hard but also brittle, so it is not readily shaped by ordinary metalworking. Finely divided osmium can oxidize slowly in air to form volatile osmium tetroxide.
Osmium metal has had limited historical use in very hard wear-resistant alloys, including early fountain-pen tips, instrument pivots, and electrical contacts, but most such uses have been replaced by other platinum-group alloys or tungsten materials. Osmium tetroxide, OsO₄, remains important in microscopy as a stain and fixative for unsaturated lipids and biological membranes. Osmium compounds are also used as specialized oxidation catalysts and reagents in organic synthesis, generally on small laboratory or fine-chemical scales.
Metallic osmium is hard, brittle and very difficult to make. Powdered osmium is easier to make but emits osmium tetroxide (OsO4) when it is exposed to the air. Unfortunately, osmium tetroxide smells bad and is very poisonous. Because of these problems, osmium is primarily used to make very hard alloys. Osmium alloys can be found in ball point pen tips, fountain pen tips, record player needles, electrical contacts and other devices where frictional wear must be minimized.
The tetroxide has been used to detect fingerprints and to stain fatty tissue for microscope slides. The metal is almost entirely used to produce very hard alloys with other metals of the platinum group for fountain pen tips, instrument pivots, phonograph needles, and electrical contacts.
Isotopes in Earth/Planetary Science
The isotope-amount ratio n(187Os)/n(186Os) in rocks can be transferred to fluids, such as magmas, groundwaters, rivers, and oceans. Variations in the inherited n(187Os)/n(186Os) ratios can provide a useful tracer for fluid sources and migration paths, including different layers of the Earth [301] G. Faure. Principles of Isotope Geology, 2nd Edition. p. 608. Wiley, New York (1986)., [504] A. Schersten. Re-Os, Pt-Os and Hf-W Isotopes and Tracing the Core in Mantle Melts, MantlePlumes.org (2014), Feb. 25; http://www.mantleplumes.org/Os-W.html., [516] A. D. Brandon, R. J. Walker. Earth. Planet. Sci. Lett.3-4 (232), 211 (2005)., [517] M. Sharma, G. J. Wasserburg, A. W. Hofmann, G. J. Chakrapani. Geochim. Cosmochim. Acta63 (23-24), 4005 (1999).. Meteorites and meteorite dust impacting the Earth have different osmium isotopic compositions than terrestrial rocks and sediments. As a result, n(187Os)/n(186Os)-ratio studies provide evidence of continuing extraterrestrial additions to the Earth over geologic time, as well as providing a method for prospecting in the sedimentary record for large meteorite impact events that may have affected life on Earth [518] F. S. Paquay, G. E. Ravizza, T. K. Dalai, B. Peucker-Ehrenbrink. Science320 (5873), 214 (2008)..
Isotopes in Geochronology
Some 187Os is radiogenic as a result of being formed by the beta decay of radioactive 187Re, which has a half-life of 4.16×1010 years. Variations in the isotope-amount ratio n(187Os)/n(186Os) and amount ratio n(187Re)/n(186Os) are used for geochronology; for example, variations in these ratios have been used to determine the ages of the Earth, Moon, and meteorites [301] G. Faure. Principles of Isotope Geology, 2nd Edition. p. 608. Wiley, New York (1986).. Kirk et al. [519] J. Kirk, J. Ruiz, J. Chesley, J. Walshe, G. England. Science297, 1856 (2002). measured rhenium-osmium isotopic abundances in gold and pyrites from conglomerates of the Central Rand Group of South Africa (Fig. IUPAC.76.1), which have produced over 48 000 metric tons of gold and have accounted for 40 percent of the world’s total historic production [520] H. E. Frimmel, W. E. L. Minter. Soc. Econ. Geol. Spec. Publ.9, 17 (2002).. The gold and rounded pyrites from the conglomerates yield an age of ~3.0×109 years. Kirk et al. find that this age is much older than that of the conglomerate, and they conclude that the gold is detrital (material wearing away by weathering or erosion) and was not deposited by later hydrothermal fluids.
Isotopes Used as a Source of Radioactive Isotope(s)
192Os can be used for the production of the medical radioisotope 195mPt via the 192Os (α, n) 195mPt reaction.
Osmium shows a wide range of oxidation states, from negative states in carbonyl complexes to the high +8 state. Osmium tetroxide, OsO₄, is the best-known compound; it is volatile, strongly oxidizing, and formed by oxidation of osmium metal or lower oxides. Osmium dioxide, OsO₂, is a stable dark oxide with rutile-type structure. Halide chemistry includes osmium tetrachloride, OsCl₄, and chloroosmate complexes such as hexachloroosmate(IV), [OsCl₆]²⁻. Organometallic and carbonyl complexes are important in coordination chemistry but are not bulk materials.
See more information at the Osmium compound page.
Compact osmium metal is relatively inert, but powders and sponges are hazardous because they can produce osmium tetroxide, OsO₄, in air. OsO₄ is highly toxic, volatile, and a strong oxidant; it can damage eyes, skin, and respiratory tissue at very low exposure levels. Osmium compounds should be treated as toxic laboratory chemicals. Natural osmium contains stable isotopes and is not a radiological hazard in ordinary material.
Concentrations in air as low as 107 g/m3 can cause lung congestion, skin damage, or eye damage. Exposure to osmium tetroxide should not exceed 0.0016 mg/m3 (8-hour time weighted average - 40-hour work week).
Osmium is a trace element in the crust and is commonly associated with platinum-group minerals in mafic and ultramafic rocks. It is highly particle-reactive in many natural settings and can be transported in detrital grains or bound to sulfides and organic-rich sediments. The rhenium-osmium isotope system is used to date some ores and sedimentary rocks. Environmental releases are normally very small, but soluble or volatile osmium compounds can be locally significant in laboratories and specialized industry.
Osmium is recovered as a minor by-product of platinum and nickel-copper ore processing rather than mined as a primary product. Separation from other platinum-group metals is technically demanding because of similar chemistry and because volatile osmium tetroxide, OsO₄, must be controlled. Demand is small and specialized, centered on laboratory reagents, catalysts, and limited alloy applications. Recycling occurs mainly through recovery of platinum-group metal residues rather than through a large independent osmium market. Substitution is common where hardness, corrosion resistance, or catalytic behavior can be supplied by iridium, ruthenium, platinum alloys, or non-precious materials.
Osmium occurs in iridosule and in platinum-bearing river sands in the Urals, North America, and South America. It is also found in the nickel-bearing ores of Sudbury, Ontario region along with other platinum metals. While the quantity of platinum metals in these ores is very small, the large tonnages of processed nickel ores make commercial recovery possible.
Osmium is a heavy element made mainly by neutron-capture processes in earlier generations of stars, with contributions from both rapid and slow neutron-capture pathways depending on isotope. It is rare in the solar system but enriched with other siderophile platinum-group elements in metallic phases. Its isotopic ratios are useful tracers in meteoritic and planetary differentiation studies.
- Osmium is usually cited as the densest naturally occurring element, very close to iridium.
- The name comes from the Greek word for smell, referring to the sharp odor of osmium tetroxide.
- Osmium tetroxide reacts with carbon-carbon double bonds, which underlies its use in staining lipids.
- Some osmiridium alloys occur naturally as hard metallic grains in placer deposits.
- The isotope ¹⁸⁷Os is the decay product of long-lived ¹⁸⁷Re.
Immagini
Proprietà
Fisiche
- Raggio atomico (empirico)
- 130 pm Confronta Raggio atomico (empirico) di tutti gli elementi →
- Raggio covalente
- 144 pm Confronta Raggio covalente di tutti gli elementi →
- Raggio di van der Waals
- 216 pm Confronta Raggio di van der Waals di tutti gli elementi →
- Raggio metallico
- 126 pm Confronta Raggio metallico di tutti gli elementi →
- Densità
- 2,25872 × 104 kg/m³ Confronta Densità di tutti gli elementi →
- Volume molare
- 0,00843 L/mol
- Fase in condizioni STP
- Solido Confronta Fase in condizioni STP di tutti gli elementi →
- Punto di fusione
- 3032,85 °C Confronta Punto di fusione di tutti gli elementi →
- Punto di ebollizione
- 5011,85 °C Confronta Punto di ebollizione di tutti gli elementi →
- Capacità termica specifica
- 0,13 J/(g·K) Confronta Capacità termica specifica di tutti gli elementi →
- Capacità termica molare
- 24,7 J/(mol·K) Confronta Capacità termica molare di tutti gli elementi →
- Struttura cristallina
- Esagonale compatta Confronta Struttura cristallina di tutti gli elementi →
Chimiche
- Elettronegatività (Pauling)
- 2,2 Confronta Elettronegatività (Pauling) di tutti gli elementi →
- Elettronegatività (Allen)
- 1,65
- Affinità elettronica
- 1,1 eV
- Energia di ionizzazione (1ª)
- 8,43823 eV Confronta Energia di ionizzazione (1ª) di tutti gli elementi →
- Energia di ionizzazione (2ª)
- 17,000059 eV Confronta Energia di ionizzazione (2ª) di tutti gli elementi →
- Energia di ionizzazione (3ª)
- 25,000086 eV Confronta Energia di ionizzazione (3ª) di tutti gli elementi →
- Energia di ionizzazione (4ª)
- 41,000141 eV Confronta Energia di ionizzazione (4ª) di tutti gli elementi →
- Energia di ionizzazione (5ª)
- 55,000189 eV Confronta Energia di ionizzazione (5ª) di tutti gli elementi →
- Stati di ossidazione
- −4, −2, −1, 0, +1, +2, +3, +4, +5, +6, +7, +8 Confronta Stati di ossidazione di tutti gli elementi →
- Elettroni di valenza
- 8 Confronta Elettroni di valenza di tutti gli elementi →
- Configurazione elettronica
- [Xe] 6s2 4f14 5d6
Termodinamiche
- Calore di fusione
- 0,32854848 eV Confronta Calore di fusione di tutti gli elementi →
- Calore di vaporizzazione
- 6,425869 eV Confronta Calore di vaporizzazione di tutti gli elementi →
- Calore di sublimazione
- 8,187801 eV
- Calore di atomizzazione
- 8,187801 eV
- Entalpia di atomizzazione
- 8,156708 eV
Nucleari
- Protoni
- 76 Confronta Protoni di tutti gli elementi →
- Neutroni
- 116 Confronta Neutroni di tutti gli elementi →
- Isotopi noti
- 43 Confronta Isotopi noti di tutti gli elementi →
- Isotopi stabili
- 0 Confronta Isotopi stabili di tutti gli elementi →
- Isotopo più stabile
- Os-192
- Anno della scoperta
- 1803
Abbondanza
- Abbondanza (crosta terrestre)
- 0,002 mg/kg Confronta Abbondanza (crosta terrestre) di tutti gli elementi →
Struttura cristallina
- Costante reticolare a
- 274 pm
Struttura elettronica
- Elettroni per guscio
- 2, 8, 18, 32, 14, 2 Confronta Elettroni per guscio di tutti gli elementi →
Identificativi
- Numero CAS
- 7440-04-2 Confronta Numero CAS di tutti gli elementi →
- Simbolo di termine
- 5D4
- InChI
- InChI=1S/Os
- Chiave InChI
- SYQBFIAQOQZEGI-UHFFFAOYSA-N
Configurazione elettronica Misurato
Os: 4f¹⁴ 5d⁶ 6s²[Xe] 4f¹⁴ 5d⁶ 6s²1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d⁶ 6s²Modello atomico
Gli isotopi modificano il numero di neutroni, la massa e la stabilità — non la configurazione elettronica di un atomo neutro.
Modello atomico schematico, non in scala.
Impronta atomica
Spettro di emissione / assorbimento
Distribuzione isotopica
Nessun isotopo stabile.
| Numero di massa | Massa atomica (u) | Abbondanza naturale | Emivita |
|---|---|---|---|
| 167 Radioattivo | 166,971549 ± 0,000078 | N/D | 839 ms |
| 161 Radioattivo | 160,98903 ± 0,00043 | N/D | 640 us |
| 203 Radioattivo | 202,992195 ± 0,000429 | N/D | 300 ms |
| 166 Radioattivo | 165,972692 ± 0,00002 | N/D | 213 ms |
| 198 Radioattivo | 197,97441 ± 0,00021 | N/D | 125 secondi |
Fase / Stato
Motivo: 3007,8 °C sotto il punto di fusione (3032,85 °C)
Schema non in scala
Punti di transizione di fase
Energie di transizione
Energia necessaria per fondere 1 mol al punto di fusione
Energia necessaria per vaporizzare 1 mol al punto di ebollizione
Energia necessaria per sublimare 1 mol al punto di sublimazione
Densità
In condizioni standard
In condizioni standard
Spettri atomici
Sono visualizzati 10 di 76. Ordinamento per carica ionica crescente.
Righe disponibili ?
| Ione | Carica | Righe totali | Probabilità di transizione | Designazioni dei livelli |
|---|---|---|---|---|
| Os I | 0 | 534 | 0 | 0 |
| Os II | +1 | 38 | 0 | 0 |
| Os III | +2 | 1061 | 1061 | 1061 |
Livelli disponibili ?
| Ione | Carica | Livelli |
|---|---|---|
| Os I | 0 | 274 |
| Os II | +1 | 40 |
| Os III | +2 | 201 |
| Os IV | +3 | 2 |
| Os V | +4 | 2 |
| Os VI | +5 | 2 |
| Os VII | +6 | 2 |
| Os VIII | +7 | 2 |
| Os IX | +8 | 2 |
| Os X | +9 | 2 |
Raggi ionici
| Carica | Coordinazione | Spin | Raggio |
|---|---|---|---|
| +4 | 6 | N/D | 63 pm |
| +5 | 6 | N/D | 57.49999999999999 pm |
| +6 | 5 | N/D | 49 pm |
| +6 | 6 | N/D | 54.50000000000001 pm |
| +7 | 6 | N/D | 52.5 pm |
| +8 | 4 | N/D | 39 pm |
Composti
Isotopi (5)
| Numero di massa | Massa atomica (u) | Abbondanza naturale | Emivita | Modalità di decadimento | |
|---|---|---|---|---|---|
| 167 Radioattivo | 166,971549 ± 0,000078 | N/D | 839 ms | α =51±0.4%β+ ? | |
| 161 Radioattivo | 160,98903 ± 0,00043 | N/D | 640 us | α ≈100% | |
| 203 Radioattivo | 202,992195 ± 0,000429 | N/D | 300 ms | β- ?β-n ? | |
| 166 Radioattivo | 165,972692 ± 0,00002 | N/D | 213 ms | α =83±0.4%β+ =17±0.4% | |
| 198 Radioattivo | 197,97441 ± 0,00021 | N/D | 125 secondi | β- =100% |
Proprietà estese
Raggi covalenti (dati estesi)
- Raggio covalente (Pyykkö)
- 129 pm
- Raggio covalente (Pyykkö, legame doppio)
- 116 pm
- Raggio covalente (Pyykkö, legame triplo)
- 109 pm
Raggi di van der Waals
- Batsanov
- 200 pm
- Alvarez
- 248 pm
- UFF
- 312 pm
- MM3
- 235 pm
Raggi atomici e metallici
- Raggio atomico (Rahm)
- 244 pm
- Raggio metallico (C12)
- 135 pm
Scale di numerazione
- Mendeleev
- 61
- Pettifor
- 62
- Glawe
- 60
Scale di elettronegatività
- Ghosh
- 0
- Miedema
- 5
- Gunnarsson–Lundqvist
- 6
- Robles–Bartolotti
- 5
Polarizzabilità e dispersione
- Polarizzabilità dipolare
- 57 a.u.
- Polarizzabilità dipolare (inc.)
- 3 a.u.
- C₆ (Gould–Bučko)
- 584 Ha·Bohr6
Parametri di Miedema
- Volume molare di Miedema
- 8,45 cm3/mol
- Densità elettronica di Miedema
- 6
Rischio di approvvigionamento ed economia
- Concentrazione della produzione
- 60
- Rischio relativo di approvvigionamento
- 8
- Distribuzione delle riserve
- 95
- Stabilità politica (principale produttore)
- 44
- Stabilità politica (principale detentore di riserve)
- 44
Transizioni di fase e allotropi
| Punto di fusione | 3306,15 K |
| Punto di ebollizione | 5281,15 K |
Categorie degli stati di ossidazione
Dati di riferimento avanzati
Costanti di schermaggio (14)
| n | Orbitale | σ |
|---|---|---|
| 1 | s | 1,4701 |
| 2 | p | 4,4502 |
| 2 | s | 19,8502 |
| 3 | d | 13,5253 |
| 3 | p | 21,7483 |
| 3 | s | 22,5727 |
| 4 | d | 37,142 |
| 4 | f | 38,8472 |
| 4 | p | 34,856 |
| 4 | s | 33,9048 |
Dettaglio dei raggi cristallini (6)
| Carica | CN | Spin | rcrystal (pm) | Origine |
|---|---|---|---|---|
| 4 | VI | 77 | from r^3 vs V plots, from metallic oxides, | |
| 5 | VI | 71,5 | estimated, | |
| 6 | V | 63 | ||
| 6 | VI | 68,5 | estimated, | |
| 7 | VI | 66,5 | estimated, | |
| 8 | IV | 53 |
Modalità di decadimento degli isotopi (58)
| Isotopo | Modalità | Intensità |
|---|---|---|
| 161 | A | 100% |
| 162 | A | 100% |
| 163 | A | 100% |
| 163 | B+ | — |
| 164 | A | 96% |
| 164 | B+ | — |
| 165 | A | 90% |
| 165 | B+ | 10% |
| 166 | A | 83% |
| 166 | B+ | 17% |
Fattori di diffusione dei raggi X (516)
| Energia (eV) | f₁ | f₂ |
|---|---|---|
| 10 | — | 1,88117 |
| 10,1617 | — | 1,93789 |
| 10,3261 | — | 1,99632 |
| 10,4931 | — | 2,05652 |
| 10,6628 | — | 2,13032 |
| 10,8353 | — | 2,20812 |
| 11,0106 | — | 2,28877 |
| 11,1886 | — | 2,37237 |
| 11,3696 | — | 2,45796 |
| 11,5535 | — | 2,53755 |
Dati aggiuntivi
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
1.5×10-3 milligrams per kilogram
Riferimenti (1)
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
Not Applicable
Riferimenti (1)
Sources
Sources of this element.
Osmium occurs in iridosule and in platinum-bearing river sands in the Urals, North America, and South America. It is also found in the nickel-bearing ores of Sudbury, Ontario region along with other platinum metals. While the quantity of platinum metals in these ores is very small, the large tonnages of processed nickel ores make commercial recovery possible.
Riferimenti (1)
- [6] Osmium https://periodic.lanl.gov/76.shtml
Riferimenti
(9)
Data deposited in or computed by PubChem
The half-life and atomic mass data was provided by the Atomic Mass Data Center at the International Atomic Energy Agency.
Element data are cited from the Atomic weights of the elements (an IUPAC Technical Report). The IUPAC periodic table of elements can be found at https://iupac.org/what-we-do/periodic-table-of-elements/. Additional information can be found within IUPAC publication doi:10.1515/pac-2015-0703 Copyright © 2020 International Union of Pure and Applied Chemistry.
The information are cited from Pure Appl. Chem. 2018; 90(12): 1833-2092, https://doi.org/10.1515/pac-2015-0703.
Thomas Jefferson National Accelerator Facility (Jefferson Lab) is one of 17 national laboratories funded by the U.S. Department of Energy. The lab's primary mission is to conduct basic research of the atom's nucleus using the lab's unique particle accelerator, known as the Continuous Electron Beam Accelerator Facility (CEBAF). For more information visit https://www.jlab.org/
The periodic table at the LANL (Los Alamos National Laboratory) contains basic element information together with the history, source, properties, use, handling and more. The provenance data may be found from the link under the source name.
The periodic table contains NIST's critically-evaluated data on atomic properties of the elements. The provenance data that include data for atomic spectroscopy, X-ray and gamma ray, radiation dosimetry, nuclear physics, and condensed matter physics may be found from the link under the source name. Ref: https://www.nist.gov/pml/atomic-spectra-database
This section provides all form of data related to element Osmium.
The element property data was retrieved from publications.