Noble metal

This periodic table shows some elements considered noble metals: green almost always, yellow usually, red sometimes, and blue only with specific definitions. Note that, although technetium and polonium may be considered noble, they are radioactive, and their decay products are not necessarily noble.

A noble metal is a metal that has a low chemical reactivity. Normally, this means it is resistant to corrosion and oxidation in air, but more specific definitions exist in different fields of chemistry, with different levels of "nobility" for different elements depending on the definition.^[1]

Gold, silver, and the platinum group metals are usually considered noble. Sometimes, mercury and copper can be regarded as noble metals; in specific cases, other elements like rhenium are added.

Metals and alloys that use passivation to resist corrosion, like nickel, aluminium, chromium, titanium, and stainless steel are not considered noble because of their other properties, like how they react with oxygen.

Noble metals are valuable, because they are not commonly found in the Earth's crust. They have many uses in everyday things including chemical engineering, electronics, and jewelry.^[2] They are used where rusting or corrosion is unacceptable, such as data connectors on computers.

Noble Metal Media

Chalcopyrite, which is copper iron sulfide (CuFeS2), is the most abundant copper ore mineral
One half of a ruthenium bar.Size ~ 40 × 15 × 10 mmWeight ~44 g
Rhodium: 1 g powder, 1g pressed cylinder, 1 g pellet.
The noble metal palladium is very similar to platinum, and, like platinum, is often used for catalysts and for jewellery. Palladium is more reactive than platinum. Palladium has excellent capability to absorb, store, and then release hydrogen.
Acanthite, or silver sulfide (Ag2S)
Osmium Os, crystals, purity ≥ 99.99%, 2.2 g. Produced by chemical transport reaction in chlorine gas
Pieces of pure iridium, 1 g, size: 1–3 mm each
Crystals of pure platinum grown by gas phase transport.