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About Osmium

Osmium Bohr

Osmium was first isolated in the form of osmium tetroxide, OsO4, and was in fact named from the Greek osme, meaning “a smell”, due to the intense odor of this compound. This compound forms spontaneously when pure osmium metal is in contact with air, and is both volatile and extremely toxic, and thus the pure metal is rarely used. Osmium is, however, the most dense naturally occurring element and imparts hardness when used in metal alloys. Hard osmium-containing alloys are used in many contexts where resistance to wear due to friction or frequent operation is desirable; this includes use in the tips of fountain pens, instrument pivots, and electrical contacts.

Despite its extreme toxicity, osmium tetroxide is the most frequently used osmium compound. It is valuable in the life sciences for staining and fixing biological tissue for electron microscopy, where it provides contrast that would otherwise be lacking when imaging substances made primarily of carbon. Additionally, it is used as a lipid stain in light microscopy and in some cases for fingerprint detection. Osmium tetroxide is also valued as a chemical catalyst in Sharpless asymmetric dihydroxylation, a reaction for which Karl Barry Sharpless won the Nobel Prize in Chemistry in 2001. The expense of the compound limits its use for this purpose to some degree, but it is considered a far superior catalyst for this process compared to the alternative, KMnO4. Finally, organometallic complexes containing osmium are under investigation for potential use in cancer treatment.

Like other platinum group metals, osmium is typically obtained for commercial use as a byproduct of nickel and copper mining and processing, but can also be obtained from ores rich in platinum and from alluvial deposits.

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High Purity (99.999%) Osmium Oxide (OsO) Powder Osmium metal is almost entirely used to produce very hard alloys with other metals of the platinum group. Osmium tetroxide has recently been used to detect fingerprints and as an aid to stain biological samples in preparation for microscopy studies . Osmium is available as metal and compounds with purities from 99% to 99.999% (ACS grade to ultra-high purity). High Purity (99.999%) Osmium (Os) Sputtering TargetElemental or metallic forms include pellets, rod, wire and granules for evaporation source material purposes.Osmium nanoparticles and nanopowders are also available. Oxides are available in powder and dense pellet form for such uses as optical coating and thin film applications. Oxides tend to be insoluble. Fluorides are another insoluble form for uses in which oxygen is undesirable such as metallurgy, chemical and physical vapor deposition and in some optical coatings. Osmium is also available in soluble forms including chlorides, nitrates and acetates. These compounds can be manufactured as solutions at specified stoichiometries.

Osmium Properties

Osmium(Os) atomic and molecular weight, atomic number and elemental symbolOsmium is a Block D, Group 8, Period 6 element. The number of electrons in each of osmium's shells is 2, 8, 18, 32, 14, 2 and its electron configuration is [Xe] 4f14 5d6 6s2. Elemental OsmiumThe osmium atom has a radius of and its Van der Waals radius is In its elemental form, CAS 7440-04-2, Osmium has a silvery blue cast apperance.Osmium has the highest melting point and the lowest vapor pressure of any of the platinum group of metals. Osmium Bohr ModelOsmium is the least abundant stable element in the earth's crust and is the densest stable element. It is found in the alloys osmiridium and iridiosmium and as an uncombined element. Osmium was first discovered by Smithson Tennant in 1803. The origin of the name Osmium comes from the Greek word osme meaning a smell or odor.

Symbol: Os
Atomic Number: 76
Atomic Weight: 190.23
Element Category: transition metal
Group, Period, Block: 8, 6, d
Color: bluish gray/ bluish-white
Other Names: Osmio
Melting Point: 3033 °C, 5491 °F, 3306 K
Boiling Point: 5012 °C, 9054 °F, 5285 K
Density: 22.59 g·cm3
Liquid Density @ Melting Point: 20 g·cm3
Density @ 20°C: 22.61 g/cm3
Density of Solid: 22610 kg·m3
Specific Heat: 0.13 (kJ/kg K)
Superconductivity Temperature: 0.66 [or -272.49 °C (-458.48 °F)] K
Triple Point: N/A
Critical Point: N/A
Heat of Fusion (kJ·mol-1): 29.3
Heat of Vaporization (kJ·mol-1): 738.06
Heat of Atomization (kJ·mol-1): 791
Thermal Conductivity: 87.6 W·m-1·K-1
Thermal Expansion: (25 °C) 5.1 µm·m-1·K-1
Electrical Resistivity: (0 °C) 81.2 nΩ·m
Tensile Strength: N/A
Molar Heat Capacity: 24.7 J·mol-1·K-1
Young's Modulus: N/A
Shear Modulus: 222 GPa
Bulk Modulus: 462 GPa
Poisson Ratio: 0.25
Mohs Hardness: 7
Vickers Hardness: 3920 MPa
Brinell Hardness: N/A
Speed of Sound: (20 °C) 4940 m·s-1
Pauling Electronegativity: 2.2
Sanderson Electronegativity: N/A
Allred Rochow Electronegativity: 1.52
Mulliken-Jaffe Electronegativity: N/A
Allen Electronegativity: N/A
Pauling Electropositivity: 1.8
Reflectivity (%): N/A
Refractive Index: N/A
Electrons: 76
Protons: 76
Neutrons: 114
Electron Configuration: [Xe] 4f14 5d6 6s2
Atomic Radius: 135 pm
Atomic Radius,
non-bonded (Å):
Covalent Radius: 144±4 pm
Covalent Radius (Å): 1.36
Van der Waals Radius: 216 pm
Oxidation States: 8, 7, 6, 5, 4, 3, 2, 1, 0, -1, -2 (mildly acidic oxide)
Phase: Solid
Crystal Structure: hexagonal close-packed
Magnetic Ordering: paramagnetic
Electron Affinity (kJ·mol-1) 106.096
1st Ionization Energy: 840 kJ·mol-1
2nd Ionization Energy: 1600 kJ·mol-1
3rd Ionization Energy: N/A
CAS Number: 7440-04-2
EC Number: 231-114-0
MDL Number: MFCD00011147
Beilstein Number: N/A
SMILES Identifier: [Os]
InChI Identifier: InChI=1S/Os
PubChem CID: 22379
ChemSpider ID: 23937
Earth - Total: 880 ppb
Mercury - Total: 670 ppb
Venus - Total: 920 ppb
Earth - Seawater (Oceans), ppb by weight: N/A
Earth - Seawater (Oceans), ppb by atoms: N/A
Earth -  Crust (Crustal Rocks), ppb by weight: 1.8
Earth -  Crust (Crustal Rocks), ppb by atoms: 0.2
Sun - Total, ppb by weight: 2
Sun - Total, ppb by atoms: 0.02
Stream, ppb by weight: N/A
Stream, ppb by atoms: N/A
Meterorite (Carbonaceous), ppb by weight: 670
Meterorite (Carbonaceous), ppb by atoms: 70
Typical Human Body, ppb by weight: N/A
Typical Human Body, ppb by atom: N/A
Universe, ppb by weight: 3
Universe, ppb by atom: 0.02
Discovered By: Smithson Tennant
Discovery Date: 1803
First Isolation: Smithson Tennant (1803)

Health, Safety & Transportation Information for Osmium

Osmium is extremely volatile and toxic in its oxide state. Safety data for Osmium and its compounds can vary widely depending on the form. For potential hazard information, toxicity, and road, sea and air transportation limitations, such as DOT Hazard Class, DOT Number, EU Number, NFPA Health rating and RTECS Class, please see the specific material or compound referenced in the Products tab. The below information applies to elemental (metallic) Osmium.

Safety Data
Material Safety Data Sheet MSDS
Signal Word Danger
Hazard Statements H228-H315-H318-H335
Hazard Codes F, Xi
Risk Codes 11-37/38-41
Safety Precautions 16-26-36/37/39
RTECS Number RN1100000
Transport Information UN 3089 4.1/PG 2
WGK Germany nwg
Globally Harmonized System of
Classification and Labelling (GHS)
Exclamation Mark-Acute Toxicity Corrosion-Corrosive to metals Flame-Flammables

Osmium Isotopes

Osmium (Os) has seven naturally occurring isotopes. Six of them are stable: 184Os, 187Os, 188Os, 189Os, 190Os, and (most abundant) 192Os. One of them, 186Os, has an extremely long half-life (2×1015 years)

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
162Os 161.98443(54)# 1.87(18) ms a to 158W 0+ N/A 1242.11 -
163Os 162.98269(43)# 5.5(6) ms a to 159W; ß+ + p to 162W; ß+ to 163Re 7/2-# N/A 1250.19 -
164Os 163.97804(22) 21(1) ms a to 160W; ß+ to 164Re 0+ N/A 1267.58 -
165Os 164.97676(22)# 71(3) ms a to 161W; ß+ to 165Re (7/2-) N/A 1275.66 -
166Os 165.972691(20) 216(9) ms a to 162W; ß+ to 166Re 0+ N/A 1283.74 -
167Os 166.97155(8) 810(60) ms a to 163W; ß+ to 167Re 3/2-# N/A 1291.82 -
168Os 167.967804(13) 2.06(6) s ß+ to 168Re; a to 164W 0+ N/A 1309.21 -
169Os 168.967019(27) 3.40(9) s ß+ to 169Re; a to 165W 3/2-# N/A 1317.29 -
170Os 169.963577(12) 7.46(23) s ß+ to 170Re; a to 166W 0+ N/A 1325.37 -
171Os 170.963185(20) 8.3(2) s ß+ to 171Re; a to 167W (5/2-) N/A 1333.45 -
172Os 171.960023(16) 19.2(5) s ß+ to 172Re; a to 168W 0+ N/A 1341.53 -
173Os 172.959808(16) 22.4(9) s ß+ to 173Re; a to 169W (5/2-) N/A 1358.92 -
174Os 173.957062(12) 44(4) s ß+ to 174Re; a to 170W 0+ N/A 1367 -
175Os 174.956946(15) 1.4(1) min ß+ to 175Re (5/2-) N/A 1375.08 -
176Os 175.95481(3) 3.6(5) min ß+ to 176Re 0+ N/A 1383.16 -
177Os 176.954965(17) 3.0(2) min ß+ to 177Re 1/2- N/A 1391.24 -
178Os 177.953251(18) 5.0(4) min ß+ to 178Re 0+ N/A 1399.31 -
179Os 178.953816(19) 6.5(3) min ß+ to 179Re (1/2-) N/A 1407.39 -
180Os 179.952379(22) 21.5(4) min ß+ to 180Re 0+ N/A 1415.47 -
181Os 180.95324(3) 105(3) min ß+ to 181Re 1/2- N/A 1423.55 -
182Os 181.952110(23) 22.10(25) h EC to 182Re 0+ N/A 1431.63 -
183Os 182.95313(5) 13.0(5) h EC to 183Re 9/2+ N/A 1439.71 -
184Os 183.9524891(14) Observationally Stable - 0+ N/A 1447.79 0.02
185Os 184.9540423(14) 93.6(5) d EC to 185Re 1/2- N/A 1455.87 -
186Os 185.9538382(15) 2.0(11)E+15 y - 0+ N/A 1463.94 1.59
187Os 186.9557505(15) Observationally Stable - 1/2- 0.06465185 1472.02 1.96
188Os 187.9558382(15) Observationally Stable - 0+ N/A 1480.1 13.24
189Os 188.9581475(16) Observationally Stable - 3/2- 0.659933 1488.18 16.15
190Os 189.9584470(16) Observationally Stable - 0+ N/A 1496.26 26.26
191Os 190.9609297(16) 15.4(1) d ß- to 191Ir 9/2- N/A 1495.02 -
192Os 191.9614807(27) Observationally Stable - 0+ N/A 1503.1 40.78
193Os 192.9641516(27) 30.11(1) h ß- to 193Ir 3/2- 0.73 1511.18 -
194Os 193.9651821(28) 6.0(2) y ß- to 194Ir 0+ N/A 1519.26 -
195Os 194.96813(54) 6.5 min ß- to 195Ir 3/2-# N/A 1527.34 -
196Os 195.96964(4) 34.9(2) min ß- to 196Ir 0+ N/A 1535.41 -
197Os 197 2.8(6) min Unknown N/A N/A N/A -