| Atomic Mass | 190.23 |
|---|---|
| Electron Configuration | [Xe]6s24f145d6 |
| Oxidation States | +4, +3 |
| Year Discovered | 1803 |
| Atomic Mass | 190.23 |
|---|---|
| Electron Configuration | [Xe]6s24f145d6 |
| Oxidation States | +4, +3 |
| Year Discovered | 1803 |
| Element Name | Osmium |
|---|---|
| Element Symbol | Os |
| InChI | InChI=1S/Os |
| InChIKey | SYQBFIAQOQZEGI-UHFFFAOYSA-N |
| Atomic Weight |
190.23(3) 190.23 190.2 190.23(3) |
|---|---|
| Electron Configuration |
[Xe]6s24f145d6 |
| Atomic Radius |
Van der Waals Atomic Radius : 216 pm (Van der Waals) Empirical Atomic Radius : 130pm (Empirical) Covalent Atomic Radius : 144(4) pm (Covalent) |
| Oxidation States |
+4, +3 8, 7, 6, 5, 4, 3, 2, 1, 0, -1, -2, -4 (a mildly acidic oxide) |
| Ground Level |
5D4 |
| Ionization Energy |
8.7 eV 8.43823 ± 0.00020 eV |
| Electronegativity |
Pauling Scale Electronegativity : 2.2(Pauling Scale) Allen Scale Electronegativity : 1.65(Allen Scale) |
| Electron Affinity |
1.1eV 1.44eV |
| Atomic Spectra |
Lines Holdings Levels Holdings |
| Physical Description |
Solid |
| Element Classification |
Metal |
| Element Period Number |
6 |
| Element Group Number |
8 |
| Density |
22.57 grams per cubic centimeter |
| Melting Point |
3306 K (3033°C or 5491°F) 3033°C |
| Boiling Point |
5285 K (5012°C or 9054°F) 5012°C |
| Estimated Crustal Abundance |
1.5×10-3 milligrams per kilogram |
| Estimated Oceanic Abundance |
Not Applicable |
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.
| Year | Atomic Weight (uncertainty) [u] | Reference |
|---|---|---|
| 1991 | 190.23(3) | https://doi.org/10.1351/pac199264101519 |
| 1969 | 190.2(1) | https://doi.org/10.1351/pac197021010091 |
| 1938 | 190.2 | https://doi.org/10.1039/JR9380001101 |
| 1934 | 191.5 | https://doi.org/10.1039/JR9340000499 |
| 1925 | 190.8 | https://doi.org/10.1039/CT9252700913 |
| 1909 | 190.9 | https://doi.org/10.1021/ja01931a001 |
| 1902 | 191.0 | https://doi.org/10.1007/BF01370337 |
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.
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.
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.
See more information at the Osmium compound page.
| CID | Name | Formula | SMILES | Molecular Weight |
|---|---|---|---|---|
| 23937 | osmium | Os | [Os] | 190.2 |
| 472184 | osmium(4+) | Os+4 | [Os+4] | 190.2 |
| 161026 | osmium-191 | Os | [191Os] | 190.960928 |
| 177536 | osmium-182 | Os | [182Os] | 181.9521 |
| 177538 | osmium-181 | Os | [181Os] | 180.9532 |
| 167415 | osmium-189 | Os | [189Os] | 188.958146 |
| 167423 | osmium-185 | Os | [185Os] | 184.954046 |
| 167510 | osmium-193 | Os | [193Os] | 192.96415 |
| 177535 | osmium-180 | Os | [180Os] | 179.9524 |
| 177683 | osmium-194 | Os | [194Os] | 193.96518 |
| 185496 | osmium(8+) | Os+8 | [Os+8] | 190.2 |
| 5461099 | osmium(2+) | Os+2 | [Os+2] | 190.2 |
| 22676905 | osmium(6+) | Os+6 | [Os+6] | 190.2 |
| 154069848 | osmium(1+) | Os+ | [Os+] | 190.2 |
| 154082846 | osmium(5+) | Os+5 | [Os+5] | 190.2 |
| 10236049 | osmium-184 | Os | [184Os] | 183.952493 |
| 46898738 | osmium-191(4+) | Os+4 | [191Os+4] | 190.960928 |
| 70674380 | osmium-187 | Os | [187Os] | 186.955750 |
| 131708377 | osmium-186 | Os | [186Os] | 185.953838 |
| 131708378 | osmium-188 | Os | [188Os] | 187.955837 |
| 131708379 | osmium-190 | Os | [190Os] | 189.958445 |
| 131708380 | osmium-192 | Os | [192Os] | 191.96148 |
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).
| Stable Isotope Count | 5 |
|---|
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], [504], [516], [517]. 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].
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]. Kirk et al. [519] 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]. 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.
![Fig. IUPAC.76.1: Cross plot of n(¹⁸⁷Os)/n(¹⁸⁸Os) isotope-amount ratio and n(¹⁸⁷Re)/n(¹⁸⁸Os) amount ratio of gold and pyrite from South Africa’s Witwatersrand Supergoup gold deposits (modified from [519]). The turquoise diamonds are gold-bearing samples from Vaal Reef, and they form an isochron with an age of about 3.0×10⁹ years. The purple filled circles are euhedral pyrites (crystals having a flat surface and sharp angles) from the Venterdorp Contact Reef, and they have a much younger age of (672 ± 510)×10⁶ a.](https://pubchem.ncbi.nlm.nih.gov/images/iupac/j_pac-2015-0703_fig_104.jpg)
192Os can be used for the production of the medical radioisotope 195mPt via the 192Os (α, n) 195mPt reaction.
| Isotope | Atomic Mass (uncertainty) [u] | Abundance (uncertainty) | |
|---|---|---|---|
| 184Os | 183.952 493(6) | 0.0002(2) | 0.0002(1) |
| 186Os | 185.953 838(5) | 0.0159(64) | 0.0159(3) |
| 187Os | 186.955 750(5) | 0.0196(17) | 0.0196(2) |
| 188Os | 187.955 837(5) | 0.1324(27) | 0.1324(8) |
| 189Os | 188.958 146(5) | 0.1615(23) | 0.1615(5) |
| 190Os | 189.958 446(5) | 0.2626(20) | 0.2626(2) |
| 192Os | 191.961 48(2) | 0.4078(32) | 0.4078(19) |
| Nuclide | Atomic Mass and Uncertainty [u] | Half Life and Uncertainty | Discovery Year | Decay Modes, Intensities and Uncertainties [%] |
|---|---|---|---|---|
| 161Os | 160.989054 ± 0.000429 [Estimated] | 640 us ± 60 | 2010 | α≈100% |
| 162Os | 161.984434 ± 0.000322 [Estimated] | 2.1 ms ± 0.1 | 1989 | α=100% |
| 163Os | 162.982462 ± 0.000322 [Estimated] | 5.7 ms ± 0.5 | 1981 | α≈100%; β+ ? |
| 164Os | 163.978073158 ± 0.000160927 | 21 ms ± 1 | 1981 | α=96±0.4%; β+ ? |
| 165Os | 164.976654 ± 0.000215 [Estimated] | 71 ms ± 3 | 1978 | α=90±0.2%; β+=10±0.2% |
| 166Os | 165.972698135 ± 0.000019287 | 213 ms ± 5 | 1977 | α=83±0.4%; β+=17±0.4% |
| 167Os | 166.971552304 ± 0.000086841 | 839 ms ± 5 | 1977 | α=51±0.4%; β+ ? |
| 167Osm | 166.971552304 ± 0.000086841 | 672 ns ± 7 | 2009 | IT=100% |
| 168Os | 167.967799050 ± 0.000010631 | 2.1 s ± 0.1 | 1977 | β+=57±0.4%; α=43±0.4% |
| 169Os | 168.967017521 ± 0.000027847 | 3.46 s ± 0.11 | 1972 | β+=86.3±0.8%; α=13.7±0.8% |
| 170Os | 169.963579273 ± 0.000010476 | 7.37 s ± 0.18 | 1972 | β+=90.5±1%; α=9.5±1% |
| 171Os | 170.963180402 ± 0.000019589 | 8.3 s ± 0.2 | 1972 | β+ ?; α=1.80±2.1% |
| 172Os | 171.960017309 ± 0.000013704 | 19.2 s ± 0.9 | 1971 | β+=98.81±1.7%; α=1.19±1.7% |
| 173Os | 172.959808387 ± 0.000016059 | 22.4 s ± 0.9 | 1971 | β+=99.6±0.2%; α=0.4±0.2% |
| 174Os | 173.957063192 ± 0.000011008 | 44 s ± 4 | 1971 | β+≈100%; α=0.024±0.7% |
| 175Os | 174.956945126 ± 0.00001264 | 1.4 m ± 0.1 | 1972 | β+=100% |
| 176Os | 175.954770315 ± 0.000011754 | 3.6 m ± 0.5 | 1970 | β+=100% |
| 177Os | 176.954957902 ± 0.000015687 | 3.0 m ± 0.2 | 1970 | β+=100% |
| 178Os | 177.953253334 ± 0.000014634 | 5.0 m ± 0.4 | 1967 | β+=100% |
| 179Os | 178.953815985 ± 0.000016645 | 6.5 m ± 0.3 | 1968 | β+=100% |
| 179Osm | 178.953815985 ± 0.000016645 | 500 ns | 1983 | IT=100% |
| 179Osn | 178.953815985 ± 0.000016645 | 783 ns ± 14 | 1983 | IT=100% |
| 180Os | 179.952381665 ± 0.000016878 | 21.5 m ± 0.4 | 1967 | β+=100% |
| 181Os | 180.953247188 ± 0.000027201 | 105 m ± 3 | 1966 | β+=100% |
| 181Osm | 180.953247188 ± 0.000027201 | 2.7 m ± 0.1 | 1966 | β+=100% |
| 181Osn | 180.953247188 ± 0.000027201 | 262 ns ± 6 | 1974 | IT=100% |
| 182Os | 181.952110154 ± 0.000023344 | 21.84 h ± 0.20 | 1950 | ε=100% |
| 182Osm | 181.952110154 ± 0.000023344 | 780 us ± 70 | 1966 | IT=100% |
| 182Osn | 181.952110154 ± 0.000023344 | 150 ns ± 10 | 1988 | IT=100% |
| 183Os | 182.953125028 ± 0.000053428 | 13.0 h ± 0.5 | 1950 | β+=100% |
| 183Osm | 182.953125028 ± 0.000053428 | 9.9 h ± 0.3 | 1958 | β+=85±0.2%; IT=15±0.2% |
| 184Os | 183.952492919 ± 0.00000089 | 11.2 Ty ± 2.3 | 1937 | IS=0.02±0.2%; α ?; 2β+ ? |
| 185Os | 184.954045969 ± 0.000000893 | 92.95 d ± 0.09 | 1947 | ε=100% |
| 185Osm | 184.954045969 ± 0.000000893 | 3.0 us ± 0.4 | 1970 | IT=100% |
| 185Osn | 184.954045969 ± 0.000000893 | 780 ns ± 50 | 1970 | IT=100% |
| 186Os | 185.953837569 ± 0.000000816 | 2.0 Py ± 1.1 | 1931 | IS=1.59±6.4%; α=100% |
| 187Os | 186.955749569 ± 0.000000791 | Stable >3.2Py | 1931 | IS=1.96±1.7%; α ? |
| 187Osm | 186.955749569 ± 0.000000791 | 112 ns ± 6 | 1964 | IT=100% |
| 187Osn | 186.955749569 ± 0.000000791 | 231 us ± 2 | 1964 | IT=100% |
| 188Os | 187.955837292 ± 0.000000788 | Stable >3.3Ey | 1931 | IS=13.24±2.7%; α ? |
| 189Os | 188.958145949 ± 0.000000715 | Stable >3.3Py | 1931 | IS=16.15±2.3%; α ? |
| 189Osm | 188.958145949 ± 0.000000715 | 5.81 h ± 0.10 | 1960 | IT≈100%; β- ? |
| 190Os | 189.958445442 ± 0.000000697 | Stable >12Ey | 1931 | IS=26.26±2%; α ? |
| 190Osm | 189.958445442 ± 0.000000697 | 9.86 m ± 0.03 | 1950 | IT=100% |
| 191Os | 190.960928105 ± 0.000000707 | 14.99 d ± 0.02 | 1940 | β-=100% |
| 191Osm | 190.960928105 ± 0.000000707 | 13.10 h ± 0.05 | 1952 | IT=100% |
| 192Os | 191.961478765 ± 0.000002484 | Stable >53Ey | 1931 | IS=40.78±3.2%; 2β- ?; α ? |
| 192Osm | 191.961478765 ± 0.000002484 | 5.94 s ± 0.09 | 1965 | IT≈100%; β- ? |
| 192Osn | 191.961478765 ± 0.000002484 | 205 ns ± 7 | 2004 | IT=100% |
| 193Os | 192.964149637 ± 0.00000249 | 29.830 h ± 0.018 | 1940 | β-=100% |
| 193Osm | 192.964149637 ± 0.00000249 | 121 ns ± 28 | 2011 | IT=100% |
| 194Os | 193.965179407 ± 0.000002579 | 6.0 y ± 0.2 | 1951 | β-=100% |
| 195Os | 194.968318000 ± 0.00006 | 6.5 m ± 1.1 | 2004 | β-=100% |
| 195Osm | 194.968318000 ± 0.00006 | 47 s ± 3 | 2012 | IT≈100%; β- ? |
| 196Os | 195.969643261 ± 0.000043 | 34.9 m ± 0.2 | 1977 | β-=100% |
| 197Os | 196.973076 ± 0.000215 [Estimated] | 93 s ± 7 | 2003 | β-=100% |
| 197Osm | 196.973076 ± 0.000215 [Estimated] | <0.1 s | IT ?; β- ? | |
| 198Os | 197.974664 ± 0.000215 [Estimated] | 125 s ± 28 | 2008 | β-=100% |
| 199Os | 198.978239 ± 0.000215 [Estimated] | 6 s ± 3 | 2008 | β-=100% |
| 200Os | 199.980086 ± 0.000322 [Estimated] | 7 s ± 4 | 2005 | β-=100% |
| 201Os | 200.984069 ± 0.000322 [Estimated] | 3 s >300ns [Estimated] | 2009 | β- ? |
| 202Os | 201.986548 ± 0.000429 [Estimated] | 2 s >300ns [Estimated] | 2009 | β- ? |
| 203Os | 202.992195 ± 0.000429 [Estimated] | 300 ms >300ns [Estimated] | 2012 | β- ?; β-n ? |
