Symbol: Ir
Date of discovery: 1803
Name origin: Greek iris
Appearance: white
Discoverer: Smithson Tennant, et al.
Obtained from: deposits with platinum
Melting point: 2739 K
Boiling point: 4701 K
Density[kg/m3]: 22650
Molar volume: 8.52 × 10-6 m3/mol
Protons/Electrons: 77
Neutrons: 115
Shell structure: 2,8,18,32,15,2
Electron configuration: [Xe]4f145d76s2
Oxidation state: 2,3,4,6
Crystal structure: cubic face centered
Iridium is used as a hardening agent for platinum and for making tools that are exposed to high temperatures, like crucibles. Iridium salts vary widely in color, which is why iridium was named after the Latin word for rainbow: iris. The KT extinction event was a period over 65 billion years ago that marked the extinction of many forms of life such as, most popularly, the dinosaurs. This time period that marks the temporal border between the Cretaceous and Tertiary eras in geological time was identified by a thin layer of clay that contained an abnormally high level of iridium. Many scientists believe that iridium originated from an asteroid or comet that was the cause of the extinction of the dinosaurs. However, because the Earth’s core is rich in iridium, other scientists argue that iridium came from volcanic origin.
