Osmium

Osmium, ₇₆Os

Osmium
Pronunciation	/ˈɒzmiəm/ ​(OZ-mee-əm)
Appearance	sillery, blue cast
Standard atomic weight Ar, std(Os)	7002190230000000000♠190.23(3)
Osmium in the periodic cairt
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Airn Cobalt Nickel Capper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Siller (element) Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gowd Mercur (element) Thallium Leid (element) Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Ununtrium Flerovium Ununpentium Livermorium Ununseptium Ununoctium Ru ↑ Os ↓ Hs rhenium ← osmium → iridium
Atomic nummer (Z)	76
Group	group 8
Period	period 6
Block	d-block
Element category	Transeetion metal
Electron confeeguration	[Xe] 4f14 5d6 6s2
Electrons per shell	2, 8, 18, 32, 14, 2
Pheesical properties
Phase at STP	solit
Meltin pynt	3306 K ​(3033 °C, ​5491 °F)
Bylin pynt	5285 K ​(5012 °C, ​9054 °F)
Density (near r.t.)	22.59 g/cm3
when liquid (at m.p.)	20 g/cm3
Heat o fusion	57.85 kJ/mol
Heat o vapourisation	738 kJ/mol
Molar heat capacity	24.7 J/(mol·K)
Vapour pressur P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 3160 3423 3751 4148 4638 5256
Atomic properties
Oxidation states	−4, −2, −1, 0, +1, +2, +3, +4, +5, +6, +7, +8 (a mildly acidic oxide)
Electronegativity	Pauling scale: 2.2
Atomic radius	empirical: 135 pm
Covalent radius	144±4 pm
Spectral lines o osmium
Ither properties
Naitural occurrence	primordial
Creestal structur	​hexagonal close-packed (hcp)
Speed o soond thin rod	4940 m/s (at 20 °C)
Thermal expansion	5.1 µm/(m·K) (at 25 °C)
Thermal conductivity	87.6 W/(m·K)
Electrical resistivity	81.2 n Ω·m (at 0 °C)
Magnetic orderin	paramagnetic
Shear modulus	222 GPa
Bulk modulus	462 GPa
Poisson ratio	0.25
Mohs haurdness	7.0
Brinell haurdness	3920 MPa
CAS Nummer	7440-04-2
History
Diskivery	Smithson Tennant (1803)
First isolation	Smithson Tennant (1803)
Main isotopes o osmium
Iso­tope Abun­dance Hauf-life (t1/2) Decay mode Pro­duct 184Os 0.02% >5.6×1013 y (β+β+) 184W (α) 180W 185Os syn 93.6 d ε 185Re 186Os 1.59% 2.0×1015 y α 182W 187Os 1.96% - (α) 183W 188Os 13.24% - (α) 184W 189Os 16.15% - (α) 185W 190Os 26.26% - (α) 186W 191Os syn 15.4 d β− 191Ir 192Os 40.78% >9.8×1012 y (β−β−) 192Pt (α) 188W 193Os syn 30.11 d β− 193Ir 194Os syn 6 y β− 194Ir
Decay modes in parentheses are predictit, but hae nae yet been observed

Osmium (frae Greek osme (ὀσμή) meanin "smell") is a chemical element wi the seembol Os an atomic nummer 76. It is a haird, brickle, blaeish-white transeetion metal in the platinum faimily an is the densest naiturally occurrin element, wi a density o 7004225900000000000♠22.59 g/cm³. It is foond as a trace element in alloys, maistly in platinum ores. Its alloys wi platinum, iridium, an ither platinum group metals are employed in fountain pen tips, electrical contacts, an ither applications whaur extreme durability an hairdness are needit.