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What is Osmium

Osmium (pronounced as OZ-mee-em) belongs to the family of transition metals and denoted by the chemical symbol Os. It has thirty-four isotopes out of which seven occur naturally with osmium-92 having an abundance of 40.78% in the earth’s crust [1, 3]. It is also available in the form of powder, bars, balls, and coins for several commercial purposes.


Where is Osmium Found

The element is found in iridomine and platinum-bearing sands of America and Urals. It is also obtained as a by-product from nickel ores [1, 4].


Origin of its Name: Its name is derived from the Greek word ‘osme’ which means ‘smell’.

When and Where was it Discovered: In 1803, the English chemist Smithson Tennant first synthesized osmium.

How was Osmium Discovered

In 1803, when Tennant added platinum to a mixture of nitric and hydrochloric acids called aqua regia, he noticed that a major portion of the metal failed to dissolve in the solution. Although many researchers assumed the residue contained graphite earlier, he conducted a further analysis to find out. After a series of treatments with acids and alkalis, he was successful in isolating two different elements, and named them iridium and osmium, respectively [1].

Osmium Metal

Position of the Element on the Periodic Table [1]

Group 8
Period 6
Block d

Properties and Characteristics of Osmium [1, 2, 3]

General Properties

Relative atomic mass/mass number/molar mass 190.23
Atomic mass/weight 190.23 atomic mass units [8]

Physical Properties

Color/appearance Bluish-white
Luster Metallic
Odor Unknown
Malleability Yes
Ductility Yes
Melting point/freezing point 3033°C (5491°F)
Boiling point 5088°C (9046°F)
Density 22.5872 g/cm3
State at normal room temperature (solid/liquid/gas) Solid
Hardness 7 Mohs
Electrical conductivity Unknown

Magnetic Properties

Magnetic ordering Paramagnetic
Magnetic susceptibility +9.9·10−6 cm3/mol at 298 K

Chemical Properties

Flammability Yes
Oxidation number Unknown
Oxidation states 8,6,4,3,2,0,-2

Atomic Data of Osmium [1, 2, 3]

Atomic number 76
Valence electrons 8
Quantum numbers
– n 5
– ℓ 2
– m -2
– m s -1/2
Electron configuration (noble gas configuration) [Xe]4f145d66s2
Crystal structure hcp (hexagonal close-packed)
Atomic structure
– Number of Electrons 76
– Number of Neutrons 16
– Number of Protons 76
Energy levels
– First Energy Level 2
– Second Energy Level 8
– Third Energy Level 18
– Fourth Energy Level 32
– Fifth Energy Level 14
– Sixth Energy Level 2
Radius of atom
– Atomic Radius 2.16 Å
– Covalent Radius 1.36 Å
Ionic charge +2
Electronegativity 2.2
Ionization energy


1st 2nd 3rd 4th 5th 6th 7th

Osmium Bar

What is Osmium Used for

  • Addition of the metal to alloys increases hardness making them useful in the manufacture of ballpoint and fountain pens, jewelry like rings, electrical contacts, record player needles, instrument pivots, and other devices prone to frequent wear and tear [1, 2].
  • Alloys containing 10% of osmium and 90% of platinum are used pacemakers and replacement heart valves [3].
  • It plays the role of an efficient catalyst in several chemical reactions [1].

Dangers and Health Hazards of Osmium

The pure metal does not pose any harmful effects unless exposed to air as it undergoes reaction to form osmium tetraoxide, a poisonous and highly reactive compound, causing lung congestion, skin irritation, and eye problems[6, 7].

Osmium Image

Interesting Facts

  • It is the densest element, approximately two times denser than lead [1].
  • Osmium is the most stable among all the elements  [5].

Osmium Ring

Osmium Price

Pure osmium generally costs between $12,000 and $14,000 per kilogram ($300 and $500 per troy ounce). Osmium-187 is a more expensive and useful isotope, costing somewhere between $15,0000 and $25,0000.

Osmium Powder



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