Wiktionary
n. In chemistry a group of elements with related properties similar to that of platinum. Notably high resistance to chemical activity, particularly oxidation and reaction with acids. The platinum group consists of the elements ruthenium, rhodium, palladium, osmium, iridium, and platinum. In the periodic table of the elements they are in period 5 or 6 and in groups 8, 9 or 10.
Wikipedia
The platinum-group metals (abbreviated as the PGMs; alternatively, the platinoids, platinides, platidises, platinum group, platinum metals, platinum family or platinum-group elements (PGEs)) 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).
The six platinum-group metals are ruthenium, rhodium, palladium, osmium, iridium, and platinum. They have similar physical and chemical properties, and tend to occur together in the same mineral deposits. However they can be further subdivided into the iridium-group platinum-group elements (IPGEs: Os, Ir, Ru) and the palladium-group platinum-group elements (PPGEs: Rh, Pt, Pd) based on their behaviour in geological systems.
The three elements above the platinum group in the traditional periodic table (iron, nickel and cobalt) are all ferromagnetic, these being the only known transition metals with this property.
Usage examples of "platinum group".
And, indeed, deep in the crust of the illuminated globe appeared a vague network of vanadiums, chromiums, and platinums, the platinum group including osmium and iridium.
In addition, it is a treasure house of raw material vital to our military preparations, chrome, diamonds, the platinum group minerals.
Because it has the highest melting point of any element in the platinum group, osmium is used to produce extremely hard alloys for instrument pivots, electrical contacts, and fountain pen tips.