All practice pages/Interatomic theory/Elements
Element 24, a transition metal
The metal that keeps stainless steel stainless, puts the shine on chrome, and makes rubies red and emeralds green.
Period 4, group 6. The other transition metals are tinted, and every cell opens its own article.
Like other transition metals, chromium loses its outer s electrons, and often some d electrons as well, to form positive ions, and it can form more than one kind.
Mined almost entirely as chromite, FeCr₂O₄, mostly in South Africa, Kazakhstan, India and Turkey. A trace of chromium in aluminum oxide makes ruby red, and in beryl it makes emerald green.
Louis-Nicolas Vauquelin found it in 1797 in crocoite, a bright orange lead mineral from Siberia, and isolated the metal the next year. He named it from the Greek chroma, color, because its compounds come in so many colors.
Most goes into stainless steel, which needs at least about 10.5% chromium to form the thin, self-healing oxide film that stops rust. Chrome plating protects and decorates car parts, faucets and tools. Chromium compounds also tan leather, color paints and glass, and preserve wood.
Chromium in the +6 state, as in chromates and dichromates, is toxic and causes cancer, so its use is tightly controlled. Chromium metal and chromium(III) compounds are far less harmful.