Knowra Iridium Iridium Iridium is a dense, hard, corrosion-resistant transition metal with atomic number 77. It is one of the platinum-group metals and among the least reactive elements.
Iridium crucible : A vessel made from iridium for high-temperature work with materials that attack ordinary crucibles. Its high melting point and chemical stability suit crystal growth and other extreme-temperature processes.
Iridium crystal structure : The arrangement of atoms in solid iridium, which crystallizes in a face-centered cubic lattice. This close-packed structure is part of the metal’s high density and mechanical behavior.
Smithson Tennant : An English chemist who discovered iridium and osmium in platinum ores in 1803. Tennant identified iridium after separating the insoluble residues left from dissolving crude platinum.
Osmium : A dense, hard transition metal with atomic number 76 and a member of the platinum-group metals. Osmium lies beside iridium in the periodic table and is often cited as the densest naturally occurring element.
Chicxulub crater : A buried impact structure beneath Mexico’s Yucatán Peninsula, formed by the asteroid impact about 66 million years ago. The crater provides a physical source for the impact event linked to iridium-rich K–Pg sediments.
Spark plug : A device that ignites fuel-air mixtures in an internal-combustion engine using an electric spark. Iridium-alloy electrodes resist erosion, allowing some spark plugs to use fine, durable tips.
Iridium oxidation states : The formal charges iridium can adopt in compounds, especially +3 and +4, with other states also known. Its compounds’ chemistry depends strongly on which oxidation state the metal occupies.
Platinum-group metal refining : The processes used to separate and purify platinum, palladium, rhodium, ruthenium, iridium, and osmium. Iridium’s discovery arose from the difficult separation of platinum-ore residues.
Platinum : A dense, malleable, corrosion-resistant transition metal with atomic number 78. Platinum is a more workable platinum-group metal, while iridium is harder and more resistant to wear.
Cretaceous–Paleogene extinction event : A mass extinction about 66 million years ago that eliminated non-avian dinosaurs and many other species. Iridium-rich boundary deposits helped connect this extinction to an extraterrestrial impact.
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