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The platinum-group metals [a] (PGMs) are six noble, precious metallic elements clustered together in the periodic table. These elements are all transition metals in the d-block (groups 8, 9, and 10, periods 5 and 6). [1] The six platinum-group metals are ruthenium, rhodium, palladium, osmium, iridium, and platinum.
Platinum is an extremely rare metal, [26] occurring at a concentration of only 0.005 ppm in Earth's crust. [27] [28] Sometimes mistaken for silver, platinum is often found chemically uncombined as native platinum and as alloy with the other platinum-group metals and iron mostly.
The source of platinum and palladium deposits is ultramafic rocks which have enough sulfur to form a sulfide mineral while the magma is still liquid. This sulfide mineral (usually pentlandite , pyrite , chalcopyrite , or pyrrhotite ) gains platinum by mixing with the bulk of the magma because platinum is chalcophile and is concentrated in sulfides.
Only gold, silver, copper and the platinum group occur native in large amounts. [citation needed] Over geological time scales, very few metals can resist natural weathering processes like oxidation, so mainly the less reactive metals such as gold and platinum are found as native metals. The others usually occur as isolated pockets where a ...
A noble metal is ordinarily regarded as a metallic element that is generally resistant to corrosion and is usually found in nature in its raw form. Gold, platinum, and the other platinum group metals (ruthenium, rhodium, palladium, osmium, iridium) are most often so classified.
Palladium, platinum, rhodium, ruthenium, iridium and osmium form a group of elements referred to as the platinum group metals (PGMs). They have similar chemical properties, but palladium has the lowest melting point and is the least dense of them.
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The radioactivity in MBq per gram of each of the platinum group metals which are formed by the fission of uranium. Of the metals shown, ruthenium is the most radioactive. Palladium has an almost constant activity, due to the very long half-life of the synthesized 107 Pd, while rhodium is the least radioactive.