Noble Metal
The noble metals are metals that are resistant to corrosion and oxidation in moist air, unlike most base metals. They tend to be precious, often due to their rarity in the Earth's crust. The noble metals are considered to be (in order of increasing atomic number) ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold.
Other sources include mercury or even rhenium as a noble metal. On the other hand, titanium, niobium, and tantalum are not included as noble metals despite the fact that they are very resistant to corrosion. Noble metals should not be confused with precious metals (although many noble metals have high value).
Read more about Noble Metal: Introduction, Electrochemistry
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