noble metal

any of a number of metals, as gold, silver, mercury, or platinum, that resist oxidation when heated in air, and solution by inorganic acids.

[1350-1400; ME: precious metal]

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▪ chemistry

      any of several metallic chemical elements that have outstanding resistance to oxidation, even at high temperatures; the grouping is not strictly defined but usually is considered to include rhenium, ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold; i.e., the metals of groups VIIb, VIII, and Ib of the second and third transition series of the periodic table.

      Silver and gold, which with copper are often called the coinage metals, and platinum, iridium, and palladium comprise the so-called precious metals, which are used in jewelry.

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