Chromium

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Attribution: Alchemist-hp

Animated Chromium

History

From the Greek word chroma, color. Chromium is a steel-gray, lustrous, hard metal that takes a high polish. Discovered in 1797 by the Frenchman Louis Nicolas Vauquelin.

Sources

The principal ore is chromite, which is found in Zimbabwe, Russia, New Zealand, Turkey, Iran, Albania, Finland, Democratic Republic of Madagascar, and the Phillippines. The metal is usually produced by reducing the oxide with aluminum.

Compounds

All compounds of chromium are colored. The most important chromates are those of sodium and potassium, the dichromates, and the potassium and ammonium chrome alums. The dichromates are used as oxidizing agents in quantitative analysis, also in tanning leather.

Other compounds are of industrial value; lead chromate is chrome yellow, a valued pigment. Chromium compounds are used in the textile industry as mordants, and by the aircraft and other industries for anodizing aluminum.

Uses

Chromium is used to harden steel, manufacture stainless steel, and form many useful alloys. It is mostly used in plating to produce a hard, beautiful surface and to prevent corrosion. Chromium gives glass an emerald green color and is widely used as a catalyst.

The refractory industry uses chromite for forming bricks and shapes, as it has a high melting point, moderate thermal expansion, and stability of crystalline structure.

General Info

AtomicNumber
24
Symbol
Cr
Name
Chromium

Atomic Info

Appearance
AtomicWeight
51.9961(6)
Color
8A99C7
ElectronicConfiguration
[Ar] 3d5 4s1
ElectronegativityInPauling
1.66
AtomicRadiusInPM
127
IonRadiusInPM
80 (+2*)
VanDerWaalsRadiusInPM
IEinKJmol
653
EAinKJmol
-64
OxidationStates
-2, -1, 1, 2, 3, 4, 5, 6
StandardState
solid
BondingType
metallic
MeltingPoint
2180
BoilingPoint
2944
Density
7.14
State
Transition metal
DiscoveredYear
Ancient