Osmium (Os)
transition-metalSolid
Standard Atomic Weight
190.23 uElectron configuration
[Xe] 6s2 4f14 5d6Melting point
3032.85 °C (3306 K)Boiling point
5011.85 °C (5285 K)Density
2.258720e+4 kg/m³Oxidation states
−4, −2, −1, 0, +1, +2, +3, +4, +5, +6, +7, +8Electronegativity (Pauling)
2.2Ionization energy (1st)
Discovery year
1803Atomic radius
130 pmDetails
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.
Images
Properties
Physical
Chemical
Thermodynamic
Nuclear
Abundance
Reactivity
N/A
Crystal Structure
Electronic Structure
Identifiers
Electron Configuration Measured
Os: 4f¹⁴ 5d⁶ 6s²[Xe] 4f¹⁴ 5d⁶ 6s²1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d⁶ 6s²Atomic model
Isotopes change neutron count, mass, and stability — not the electron configuration of a neutral atom.
Schematic atomic model, not to scale.
Atomic Fingerprint
Emission / Absorption Spectrum
Isotope Distribution
No stable isotopes.
| Mass number | Atomic mass (u) | Natural abundance | Half-life |
|---|---|---|---|
| 167 Radioactive | 166.971549 ± 0.000078 | N/A | 839 ms |
| 161 Radioactive | 160.98903 ± 0.00043 | N/A | 640 us |
| 203 Radioactive | 202.992195 ± 0.000429 | N/A | 300 ms |
| 166 Radioactive | 165.972692 ± 0.00002 | N/A | 213 ms |
| 198 Radioactive | 197.97441 ± 0.00021 | N/A | 125 seconds |
Phase / State
Reason: 3007.8 °C below melting point (3032.85 °C)
Schematic, not to scale
Phase transition points
Transition energies
Energy required to melt 1 mol at melting point
Energy required to vaporize 1 mol at boiling point
Energy required to sublime 1 mol at sublimation point
Density
At standard conditions
At standard conditions
Atomic Spectra
Showing 10 of 76 Atomic Spectra. Sorted by ion charge (ascending).
Lines Holdings ?
| Ion | Charge | Total lines | Transition probabilities | Level designations |
|---|---|---|---|---|
| Os I | 0 | 534 | 0 | 0 |
| Os II | +1 | 38 | 0 | 0 |
| Os III | +2 | 1061 | 1061 | 1061 |
Levels Holdings ?
| Ion | Charge | Levels |
|---|---|---|
| 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 |
Ionic Radii
| Charge | Coordination | Spin | Radius |
|---|---|---|---|
| +4 | 6 | N/A | 63 pm |
| +5 | 6 | N/A | 57.49999999999999 pm |
| +6 | 5 | N/A | 49 pm |
| +6 | 6 | N/A | 54.50000000000001 pm |
| +7 | 6 | N/A | 52.5 pm |
| +8 | 4 | N/A | 39 pm |
Compounds
Isotopes (5)
| Mass number | Atomic mass (u) | Natural abundance | Half-life | Decay mode | |
|---|---|---|---|---|---|
| 167 Radioactive | 166.971549 ± 0.000078 | N/A | 839 ms | α =51±0.4%β+ ? | |
| 161 Radioactive | 160.98903 ± 0.00043 | N/A | 640 us | α ≈100% | |
| 203 Radioactive | 202.992195 ± 0.000429 | N/A | 300 ms | β- ?β-n ? | |
| 166 Radioactive | 165.972692 ± 0.00002 | N/A | 213 ms | α =83±0.4%β+ =17±0.4% | |
| 198 Radioactive | 197.97441 ± 0.00021 | N/A | 125 seconds | β- =100% |
Extended Properties
Covalent Radii (Extended)
Van der Waals Radii
Atomic & Metallic Radii
Numbering Scales
Electronegativity Scales
Polarizability & Dispersion
Miedema Parameters
Supply Risk & Economics
Phase Transitions & Allotropes
| Melting point | 3306.15 K |
| Boiling point | 5281.15 K |
Oxidation State Categories
Advanced Reference Data
Screening Constants (14)
| n | Orbital | 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 |
Crystal Radii Detail (6)
| Charge | CN | Spin | rcrystal (pm) | Origin |
|---|---|---|---|---|
| 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 |
Isotope Decay Modes (58)
| Isotope | Mode | Intensity |
|---|---|---|
| 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% |
X‑ray Scattering Factors (516)
| Energy (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 |
Additional Data
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
1.5×10-3 milligrams per kilogram
References (1)
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
Not Applicable
References (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.
References (1)
- [6] Osmium https://periodic.lanl.gov/76.shtml
References
(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.