Osmium, Os

Osmium is a chemical element that has the symbol Os and atomic number 76. Osmium is a hard, brittle, blue-gray or blue-black transition metal in the platinum family, and is one of the densest natural elements, competing for this status with iridium. Osmium is used in alloys with platinum, iridium and other platinum group metals. Osmium is found in nature as an alloy in platinum ore. Alloys of osmium are employed in fountain pen tips, electrical contacts and in other applications where extreme durability and hardness are needed.

Technical Data
Symbol Os Melting point / °C 3045(+/-30)
Atomic number 76 Boiling point / °C 5025(+/-100)
No. of naturally occurring isotopes 7 ΔHfus/kJmol-1 31.7
Atomic weight 190.2 ΔHvap/kJmol-1 738
Electronic configuration [Xe]4fJ45d66s2 ΔHf(monoatomic gas)/kJmol-1 791 (+/-13)
Metal radius(12-coordinate)/pm 135 Electrical resistivity  
Ionic radius(4-coordinate)/pm VIII 39 (20°C)/μohm cm 8.12
Ionic radius(6-coordinate)/pm VII 52.5 Electronegativity χ 2.2
Ionic radius(6-coordinate)/pm VI 54.5 Ionization energy/kJmol-1 I 840
Ionic radius(6-coordinate)/pm V 57.5 Ionization energy/kJmol-1 II 1600
Ionic radius(6-coordinate)/pm IV 63 Ionization energy/kJmol-1 III 2400
Density (20°C)/gcm-3 22.57    
Evaporation Techniques
Temperature (oC) @Vap. Pressure Techniques Remarks
10-8 Torr 10-6 Torr 10-4 Torr Electron Beam Crucible Coil Boat
2170 2430 276 Fair - - -  

O1-10000-P -60 mesh
O1-10001-P -325 mesh