Iridium (Ir)

by Trevin Hertzog

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History of Iridium

Iridium was founded in France, England by a chemist named Smithson Tennant. He discovered this element in 1803, in the residue left when crude platinum had been dissolved in aqua regia (a mixture of hydrochloric acid and nitric acid). Tennant also discovered the element osmium at the same time.

It is found uncombined in nature in sediments that were deposited by rivers. It is commercially recovered as a by-product of nickel refining.

About Iridium

Its location on the Periodic Table is Valence 6, Block d, Group 9, and Period 6. When you look at this element, you might be able to figure out that its atomic structure has an Atomic number, Protons, and even Electrons number of 77. Also a Mass number of 192.22, and 115.22 Neutrons.


  • Compass bearings
  • Pen tips
  • Standard meter bar
  • Contacts in spark plugs


  • Ir-193


  • Standard meter bar, which is an alloy of 90% Platinum and 10% Iridium
  • Used in special alloys
  • Forms an alloy with Osmium

Unique facts

The name Iridium is derived from the Greek goddess of the rainbow, known as Iris. This is because of the high amounts of salt in its composition, that make objets colorful. Such as a dragon flies' wings.

Iridium is one of the rarest elements on earth, and can be found in a thin layer within the earth's crust.

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Physical & Chemical Properties


Atomic Mass: 192.217 Atomic Radius (pm): 180pm Density: 22.650 g/cc

Melting Point: 2466 C (4471 F) Boiling Point: 4428 C (8002 F)

Appearance: Jagged/bumpy, weirdly shaped, & silver coloring

At room temp. (22 C): solid Hardness: Extremely hard Malleability: malleable

Conductivity: Conductor as solid, liquid not so good conductors

Unique property: highly colored salts & is one of the most corrosion- resistant metals


Flammability: Can be flammable when in finely derived dusts

Reactivity: Low reactivity (like gold), low toxicity, finely derived dusts are much more reactive

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