Chromium [Cr] (CAS-ID: 7440-47-3 ) locate me
An: 24 N: 28 Am: 51.9961
Group No: 6  Group Name: (none)
Block: d-block  Period: 4
State: solid at 298 K
Colour: silvery metallic Classification: Metallic
Boiling Point: 2945K (2671'C)
Melting Point: 2130K (1907'C)
Density: 7.15g/cm3
Shell Structure diagram | Atomic Radius diagram
Isotopes | More Info
Discovery Information
Who: Louis Vauquelin
When: 1797
Where: France
Name Origin
Greek: chroma (colour). Due to the many colourful compounds that can be made from it.
Sources
Does not occur free in nature. Chromite [Fe,Mg(CrO4)] is its most important mineral. Chromium ores are mined today in South Africa, Zimbabwe, Finland, India, Kazakihstan and the Philippines. Reserves are estimated at over 1 billion tonnes.
Uses
Used to make stainless steel. Also used in plating for car parts, magnetic tape, tools, knives, camouflage paint, stereos, and lasers. It gives rubies and emeralds their colour.
Chromium(VI) oxide (CrO3) is used to manufacture magnetic tape, where its higher coercivity than iron oxide tapes gives better performance.
Notes
Chromium metal and chromium(III) compounds are not usually considered health hazards, but hexavalent chromium (chromium VI) compounds can be toxic if orally ingested or inhaled. The lethal dose of poisonous chromium (VI) compounds is about one half teaspoon of material. Most chromium (VI) compounds are irritating to eyes, skin and mucous membranes. Chronic exposure to chromium (VI) compounds can cause permanent eye injury, unless properly treated. Chromium(VI) is an established human carcinogen.
World Health Organization recommended maximum allowable concentration in drinking water for chromium (VI) is 0.05 milligrams per liter.
Images
Chromium from China Chromium from China