Chromium
Atomic Number: 24
Symbol: Cr
Atomic Weight: 51.9961
Discovery: Louis Vauquelin 1797 (France)
Electron Configuration: [Ar] 4s1 3d5
Word Origin: Greek chroma: color
Properties: Chromium has a melting point of 1857+/-20°C, boiling point of 2672°C, specific gravity of 7.18 to 7.20 (20°C), with valences usually 2, 3, or 6. The metal is a lustous steel-gray color which takes a high polish. It is hard and resistant to corrosion. Chromium has a high melting point, stable crystalline structure, and moderate thermal expansion. All chromium compounds are colored. Chromium compounds are toxic.
Uses: Chromium is used to harden steel. It is a component of stainless steel and many other alloys. The metal is commonly used for plating to produce a shiny, hard surface that is resistant to corrosion. Chromium is used as a catalyst. It is added to glass to produce an emerald green color. Chromium compounds are important as pigments, mordants, and oxidizing agents.
Sources: The principal ore of chromium is chromite (FeCr2O4). The metal may be produced by reducing its oxide with aluminum.
Element Classification: Transition Metal
Density (g/cc): 7.18
Melting Point (K): 2130
Boiling Point (K): 2945
Appearance: very hard, crystalline, steel-grayish metal
Atomic Radius (pm): 130
Atomic Volume (cc/mol): 7.23
Covalent Radius (pm): 118
Ionic Radius: 52 (+6e) 63 (+3e)
Specific Heat (@20°C J/g mol): 0.488
Fusion Heat (kJ/mol): 21
Evaporation Heat (kJ/mol): 342
Debye Temperature (K): 460.00
Pauling Negativity Number: 1.66
First Ionizing Energy (kJ/mol): 652.4
Oxidation States: 6, 3, 2, 0
Lattice Structure: Body-Centered Cubic
Lattice Constant (Å): 2.880
References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Lange's Handbook of Chemistry (1952), CRC Handbook of Chemistry & Physics (18th Ed.)
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