OSMIUM

Introduction

Atomic Number: 76
Group: 8 or VIII B
Atomic Weight: 190.23
Period: 6
CAS Number: 7440-04-02

Classification

Chalcogen
Halogen
Noble Gas
Lanthanoid
Actinoid
Rare Earth Element
Platinum Group Metal
Transuranium
No Stable Isotopes
Solid
Liquid
Gas
Solid (Predicted)

Description • Uses/Function

Discovered in 1803 by Tennant in the residue left when crude platinum is dissolved by aqua regia. Osmium occurs in iridosmine and in platinum-bearing river sands of 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 nickel ores processed make commercial recovery possible. 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 powder can be sintered in a hydrogen atmosphere at a temperature of 2000°C. The solid metal is not affected by air at room temperature, but the powdered or spongy metal slowly gives off osmium tetroxide, which is a powerful oxidizing agent and has a strong smell. The tetroxide is highly toxic, and boils at 130°C (760 mm). Concentrations in air as low as 10^–7 g/m^3 can cause lung congestion, skin damage, or eye damage. 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. The price of 99.9% pure osmium powder — the form usually supplied commercially — is about $100/g, depending on quantity and supplier. Natural osmium contains seven isotopes, one of which, 186Os, is radioactive with a very long half-life. Thirty four other isotopes and isomers are known, all of which are radioactive.The measured densities of iridium and osmium seem to indicate that osmium is slightly more dense than iridium, so osmium has generally been credited with being the heaviest known element. Calculations of the density from the space lattice, which may be more reliable for these elements than actual measurements, however, give a density of 22.65 for iridium compared to 22.61 for osmium. At present, therefore, we know either iridium or osmium is the heaviest element, but the data do not allow selection between the two. 1

Physical Properties

Melting Point:2*  3033 °C = 3306.15 K = 5491.4 °F
Boiling Point:2* 5012 °C = 5285.15 K = 9053.6 °F
Sublimation Point:2 
Triple Point:2 
Critical Point:2 
Density:3  22.59 g/cm3

* - at 1 atm

Electron Configuration

Electron Configuration: [Xe] 6s2 4f14 5d6
Block: d
Highest Occupied Energy Level: 6
Valence Electrons: 

Quantum Numbers:

n = 5
ℓ = 2
m = -2
ms = -½

Bonding

Electronegativity (Pauling scale):4 2.2
Electropositivity (Pauling scale): 1.8
Electron Affinity:5 1.1 eV
Oxidation States: +4,6,8
Work Function:6 4.83 eV = 7.73766E-19 J

Ionization Potential   eV 7  kJ/mol  
Ionization Potential   eV 7  kJ/mol  
Ionization Potential   eV 7  kJ/mol  
1 8.4382    814.2

Thermochemistry

Specific Heat: 0.130 J/g°C 8 = 24.730 J/mol°C = 0.031 cal/g°C = 5.911 cal/mol°C
Thermal Conductivity: 87.6 (W/m)/K, 27°C 9
Heat of Fusion: 31.8 kJ/mol 10 = 167.2 J/g
Heat of Vaporization: 746 kJ/mol 11 = 3921.6 J/g
State of Matter Enthalpy of Formation (ΔHf°)12 Entropy (S°)12 Gibbs Free Energy (ΔGf°)12
(kcal/mol) (kJ/mol) (cal/K) (J/K) (kcal/mol) (kJ/mol)
(s) 0 0 7.8 32.6352 0 0
(g) 189 790.776 46.000 192.464 178 744.752

Isotopes

Nuclide Mass 13 Half-Life 13 Nuclear Spin 13 Binding Energy
162Os 161.98443(54)# 1.87(18) ms 0+ 1,266.72 MeV
163Os 162.98269(43)# 5.5(6) ms 7/2-# 1,274.79 MeV
164Os 163.97804(22) 21(1) ms 0+ 1,292.18 MeV
165Os 164.97676(22)# 71(3) ms (7/2-) 1,300.25 MeV
166Os 165.972691(20) 216(9) ms 0+ 1,308.32 MeV
167Os 166.97155(8) 810(60) ms 3/2-# 1,316.39 MeV
168Os 167.967804(13) 2.06(6) s 0+ 1,333.78 MeV
169Os 168.967019(27) 3.40(9) s 3/2-# 1,341.85 MeV
170Os 169.963577(12) 7.46(23) s 0+ 1,349.92 MeV
171Os 170.963185(20) 8.3(2) s (5/2-) 1,357.99 MeV
172Os 171.960023(16) 19.2(5) s 0+ 1,366.07 MeV
173Os 172.959808(16) 22.4(9) s (5/2-) 1,383.45 MeV
174Os 173.957062(12) 44(4) s 0+ 1,391.52 MeV
175Os 174.956946(15) 1.4(1) min (5/2-) 1,399.59 MeV
176Os 175.95481(3) 3.6(5) min 0+ 1,407.67 MeV
177Os 176.954965(17) 3.0(2) min 1/2- 1,415.74 MeV
178Os 177.953251(18) 5.0(4) min 0+ 1,423.81 MeV
179Os 178.953816(19) 6.5(3) min (1/2-) 1,431.88 MeV
180Os 179.952379(22) 21.5(4) min 0+ 1,439.95 MeV
181Os 180.95324(3) 105(3) min 1/2- 1,448.02 MeV
182Os 181.952110(23) 22.10(25) h 0+ 1,456.09 MeV
183Os 182.95313(5) 13.0(5) h 9/2+ 1,464.17 MeV
184Os 183.9524891(14) STABLE 0+ 1,472.24 MeV
185Os 184.9540423(14) 93.6(5) d 1/2- 1,480.31 MeV
186Os 185.9538382(15) 2.0(11)E+15 a 0+ 1,488.38 MeV
187Os 186.9557505(15) STABLE 1/2- 1,496.45 MeV
188Os 187.9558382(15) STABLE 0+ 1,504.52 MeV
189Os 188.9581475(16) STABLE 3/2- 1,512.59 MeV
190Os 189.9584470(16) STABLE 0+ 1,520.66 MeV
191Os 190.9609297(16) 15.4(1) d 9/2- 1,519.42 MeV
192Os 191.9614807(27) STABLE 0+ 1,527.49 MeV
193Os 192.9641516(27) 30.11(1) h 3/2- 1,535.56 MeV
194Os 193.9651821(28) 6.0(2) a 0+ 1,543.63 MeV
195Os 194.96813(54) 6.5 min 3/2-# 1,551.71 MeV
196Os 195.96964(4) 34.9(2) min 0+ 1,559.78 MeV
197Os 2.8(6) min
Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses. 13

Abundance

Earth -  Crust:  0.0015 mg/kg = 0.00000015% 14
Earth -  Total:  880 ppb 15
Mercury -  Total:  670 ppb 15
Venus -  Total:  920 ppb 15
Chondrites - Total: 0.54 (relative to 106 atoms of Si) 16

Compounds

Safety Information


Material Safety Data Sheet - ACI Alloys, Inc.

For More Information

External Links:

Sources

(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:21.
(2) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:132.
(3) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 4:39-4:96.
(4) - Dean, John A. Lange's Handbook of Chemistry, 11th ed.; McGraw-Hill Book Company: New York, NY, 1973; p 4:8-4:149.
(5) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 10:147-10:148.
(6) - Speight, James. Lange's Handbook of Chemistry, 16th ed.; McGraw-Hill Professional: Boston, MA, 2004; p 1:132.
(7) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(8) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:133.
(9) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(10) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(11) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(12) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:4-9:94.
(13) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).
(14) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 14:17.
(15) - Morgan, John W. and Anders, Edward, Proc. Natl. Acad. Sci. USA 77, 6973-6977 (1980)
(16) - Brownlow, Arthur. Geochemistry; Prentice-Hall, Inc.: Englewood Cliffs, NJ, 1979, pp 15-16.