Iridium: Properties, Health Effects & Uses

Iridium is a chemical element with atomic number 77 and the symbol Ir. It is a platinum group transition metal that is highly hard, brittle, and silvery-white.

• Iridium is the second-densest naturally occurring metal (after osmium).
• It has a density of 22.65 g/cm3 at ambient temperature.
• Even at temperatures as high as 2000 °C, it is the most corrosion-resistant metal.
• Solid iridium is only corroded by a few molten salts and halogens; finely split iridium dust is far more reactive and volatile.
• The chemical element was discovered by Smithson Tennant in 1803.
• It is most commonly used in the automotive industry, electronics industry, and chemical industry.
• Iridium is one of the most important components used in OLED.

 

Key Terms: Iridium, Atomic Number, Transition Metal, Platinum, Halogens, Corrosion, Isotopes, Osmium, Electron, Hydrochloric Acid, Halogen, Oxygen, Periodic Table, Electronic Configuration

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What is Iridium?

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Iridium is an organic compound that is one of the rarest transition metals that is used as a hardening agent for platinum. Highly corrosive metal of the periodic table, the compound is most commonly found in meteorites.

• Iridium prices have surged in recent times due to an increase in demand in the technology industry.
• The compound becomes ductile in the temperature range of 1200 to 1500 degree C.
• It is used for the recrystallization of semiconductor at high temperatures.
• Chlorides and iodides are important components of iridium.
• It has the second highest modulus of elasticity among the list of metals.

The tabulated detail about Iridium is as follows:

Iridium

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Discovery Of Iridum

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Smithson Tennant (1761–1815), a British chemist, made the discovery of Iridium. He treated the insoluble residue powder with alkali and acids alternately.

• Later, he produced a volatile new oxide.
• He thought to be of this new metal, which he named ptene after the Greek word v ptnós, which means "winged." 
• Tennant, who had access to a far larger volume of residue, continued his investigation.
• In the black residue, he found the two previously unknown elements, iridium and osmium. 
• A series of reactions with sodium hydroxide and hydrochloric acid yielded dark red crystals (most likely Na₂[IrCl₆]nH₂O).
• Many of the salts he got were brightly coloured.
• He named it after Iris, the Greek winged goddess of the rainbow and messenger of the Olympian gods.

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Occurrence of Iridium

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Iridium is found in the highest quantities in three types of geologic formations inside the Earth's crust. These three types include igneous deposits (crustal intrusions from below), impact craters, and deposits reworked from one of the previous structures.

• The Bushveld igneous complex in South Africa has the largest known primary reserves.

Large copper-nickel deposits near Norilsk in Russia and the Sudbury Basin (also an impact crater) in Canada are also important sources of iridium.

• Secondary deposits of iridium, along with platinum and other platinum group metals, can be discovered in alluvial deposits.
• Platinum-group metals may still be found in alluvial deposits utilized by pre-Columbian inhabitants in Colombia's Chocó Department.

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Properties of Iridium

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The properties of Iridium are as follows:

Physical Properties Of Iridium

The physical properties of Iridium are as follows:

• Iridium is a white metal that resembles like platinum but has a faint yellowish hue. 
• It is a member of the platinum group of metals. 
• Solid iridium is difficult to manufacture, mould, or manipulate due to its hardness, brittleness, and extremely high melting temperature.

It is the only metal that can maintain acceptable mechanical characteristics in the air at temperatures exceeding 1,600 degrees Celsius (2,910 degrees Fahrenheit). 

• It has the tenth-highest boiling point of all elements, and at temperatures below 0.14 K, it becomes a superconductor.
• The melting and boiling points of iridium are 2719 K and 4403 K, respectively.
• The electronic configuration of the compound is [Xe] 4f¹⁴ 5d⁷ 6s².
• Iridium generates compounds with oxidation levels ranging from 3 to 9, with +3 and +4 being the most frequent.
• Compounds of the high +6 oxidation state are rare.

The physical properties of Iridium are as follows:

Chemical Properties Of Iridium

Iridium is the most corrosion-resistant metal known: at high temperatures. It is unaffected by practically any acid, aqua regia, molten metals, or silicates.

• At higher temperatures, it can be attacked by various molten salts, such as sodium cyanide and potassium cyanide.
• It can also be reacted by oxygen and halogens (especially fluorine).
• At atmospheric pressure, iridium combines immediately with sulfur to produce iridium disulfide.

Other chemical properties of Iridium are as follows:

Reaction with Oxygen

When Iridium is heated with oxygen it will form iridium (IV) oxide, IrO₂.

Ir + O₂→ IrO₂ [black]

Reaction with Water

Iridium is a type of metal that does not react with water under normal conditions.

Reaction with Halogens

When iridium react with halogen fluorine then it will form highly corrosive iridium(VI) fluoride, IrF₆.

Ir + 3F₂ → IrF₆ [yellow]

Reaction with other halogen which are as follows:

2Ir + 3Cl₂ → 2IrCl₃ [red]

2Ir + 3Br₂ → 2IrBr₃ [red-brown]

2Ir + 3I₂ → 2IrI₃ [dark brown]

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Isotopes of Iridium

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The stable isotopes of iridium are ¹⁹¹Ir and ¹⁹³Ir, which have natural abundances of 37.3 per cent and 62.7 per cent, respectively. At least 32 metastable isomers with mass numbers ranging from 164 to 197 have been identified.

• The most stable is ^192m2Ir, which decays through isomeric transition with a half-life of 241 years.
• It is more stable in its ground state than any of iridium's synthetic isotopes.

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Applications Of Iridium

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Iridium demand increased dramatically from 2.5 metric tonnes in 2009 to 10.4 metric tonnes in 2010. It primarily increase in electronics-related applications from 0.2 to 6 metric tonnes.

• Iridium crucibles are commonly used for growing large, high-quality single crystals, and demand for them has increased dramatically.
• Compass bearings and balances are made out of osmium–iridium.
• The compound is used as a source of energy in radiography. 

The alloys are utilized for long-life aviation engine parts, and iridium–titanium alloy is used for deep-water pipelines due to its corrosion resistance. In platinum alloys, the compound is also utilized as a hardening agent.

• It is used for tipping fountain pen nibs.
• The compound is used in Space vehicles and Satellites.
• They are used in multi-pored spinnerets, through which a plastic polymer melt is extruded to make rayon strands.
• It is used in the production of tips of spark plugs.

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Iridium Effects

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Since it lacks reactivity with tissues, iridium in bulk metallic form is neither physiologically relevant nor dangerous to health. Human tissue contains only around 20 parts per trillion of iridium. 

• Finely split iridium powder, like other metals, may be hazardous to handle since it is irritating and can burn in the air. 

The toxicity of iridium compounds is poorly understood because it is used so seldom that few individuals come into contact with it, and those who do only in extremely minute doses. 

• However, soluble salts, such as iridium halides, may be harmful due to other elements or iridium. 
• At the same time, most iridium compounds are insoluble, making absorption into the body difficult.

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Things to Remember

• Iridium is a chemical element with atomic number 77, which is a highly hard, brittle, and silvery-white compound.
• It is found in igneous deposits (crustal intrusions from below), impact craters, and deposits.
• The compound is a white metal that is the most corrosion-resistant metal.
• It does not form any type of binary hydride.
• Exposure of the compound to the skin will result in burning and radiation sickness.