OSMIUM

76 Os 190.23(3)

A Little Key data

Name: osmium
Symbol: Os
Atomic number: 76
Atomic weight: 190.23 (3) g
CAS Registry ID: 7440-04-2
Group number: 8
Group name: Precious metal
Period number: 6
Block: d-block

Description

Osmium - Os

General Information

Discovery

Osmium was discovered by S. Tennant in 1803 in London.

Appearance

Osmium is lustrous, bluish-white, extremely hard and has a pungent smell.

Source

Osmium occurs in the free state and in the mineral osmiridium, but commercial recovery is from the wastes of nickel refining.

Uses

Osmium is almost entirely used to produce very hard alloys for fountain pen tips, instrument pivots, needles and electrical contacts.

Biological Role

Osmium has no known biological role, but is very toxic, and can cause lung, skin and eye damage.

General Information

Osmium metal is unaffected by air, water and acids, but dissolves in molten alkalis. The powdered metal slowly gives off osmium (VIII) oxide, the source of its pungent odor.

Price

Extra pure Osmium of 190.2 mol. wt. is available from Sigma-Aldrich for $140.35 per gram.

	More Physical Information
	Melting Point/K		3327
	Boiling Point/K		5300
	Density/kg m^-3		22590 (293K)
	Ground State Electron Configuration		[Xe]4f¹⁴5d⁶6s²
	Electron Affinity(M-M^-)/kJ mol^-1		139

Key Isotopes
nuclide	¹⁸⁴Os	¹⁸⁵Os	¹⁸⁶Os	¹⁸⁷Os	¹⁸⁸Os
atomic mass	183.9		185.9	186.9	187.9
natural abundance	0.02%	0%	1.58%	1.6%	13.3%
half-life	stable	9.6 days	stable	stable	stable

nuclide	¹⁸⁹Os	¹⁹⁰Os	¹⁹¹Os	¹⁹²Os
atomic mass	188.9	189.9		191.9
natural abundance	16.1%	26.4%	0%	41%
half-life	stable	stable	15 days	stable

Other Information
Enthalpy of Fusion/kJ mol^-1		29.3
Enthalpy of Vaporization/kJ mol^-1		738

Oxidation States
main	Os^IV
others	Os^-II, Os^O, Os^I, Os^II, Os^III,
	Os^V, Os^VI, Os^VII, Os^VIII

	Ionisation Energies/kJ mol-1
	M - M⁺	840
	M⁺ - M²⁺	1600
	M²⁺ - M³⁺	2400
	M³⁺ - M⁴⁺	3900
	M⁴⁺ - M⁵⁺	5200
	M⁵⁺ - M⁶⁺	6600
	M⁶⁺ - M⁷⁺	8100
	M⁷⁺ - M⁸⁺	9500
	M⁸⁺ - M⁹⁺
	M⁹⁺ - M¹⁰⁺

Isolation

It would not normally be necessary to make a sample of osmium in the laboratory as the metal is available, at a price, commercially. The industrial extraction of osmium is complex as the metal occurs in ores mixed with other metals such as ruthenium, rhodium, palladium, silver, platinum, and gold. Sometimes extraction of the precious metals such as iridium, rhodium, platinum and palladium is the main focus of a particular industrial operation while in other cases it is a byproduct. The extraction is complex because of the other metals present and only worthwhile since osmium is useful as a specialist metal and is the basis of some catalysts in industry.

Preliminary treatment of the ore or base metal byproduct is required to remove silver, gold, palladium, and platinum. The residue is melted with sodium bisulphate (NaHSO₄) and the resulting mixture extracted with water to give a solution containing rhodium sulphate, Rh₂(SO₄)₃. The insoluble residue contains the osmium. The residue is melted with Na₂O₂ and extracted into water to extract the ruthenium and osmium salts (including [RuO₄]^2- and [OsO₄(OH)₂]^2-). The residue contains iridium oxide, IrO₂. Reaction of the salt with chlorine gas gives the volatile oxides RuO₄ and OsO₄. The osmium oxide is dissolved by treatment with alcoholic sodium hydroxide to form Na₂[OsO₂(OH)₄], and the osmium precipiated out as pure OsCl₂O₂(NH₃)₄ by treatment with NH₄Cl. Evaporation to dryness and burning under hydrogen gas gives pure osmium.

The popular death-metal band OSMIUM

Brought to you by Jason Woo, friend of chemistry

More information on Osmium available at:

http://www.efunda.aoM/materials/elements/element_info.cfm?Element_ID=Os

www.webelements.com

www.osmium.demon.co.uk

www.iLoveOsmium.com

HEY KIDS!!!!

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That Shania Twain, the members of 'N Sync and Sam Donaldson have all said that Osmium is their favorite chemical element!