Chromium

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Chromium,  24Cr
Chromium crystals and 1cm3 cube.jpg
General properties
Appearance sillery metallic
Staundart atomic wecht (Ar, staundart) 51.9961(6)
Chromium in the periodic cairt
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Airn Cobalt Nickel Capper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Siller (element) Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gowd Mercur (element) Thallium Leid (element) Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Ununtrium Flerovium Ununpentium Livermorium Ununseptium Ununoctium
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Cr

Mo
vanadiumchromiummanganese
Atomic nummer (Z) 24
Group group 6
Period period 4
Element category   transition metal
Block d-block
Electron confeeguration [Ar] 3d5 4s1
Electrons per shell
2, 8, 13, 1
Pheesical properties
Phase (at STP) solit
Meltin pynt 2180 K ​(1907 °C, ​3465 °F)
Bylin pynt 2944 K ​(2671 °C, ​4840 °F)
Density (near r.t.) 7.19 g/cm3
when liquid (at m.p.) 6.3 g/cm3
Heat o fusion 21.0 kJ/mol
Heat o vapourisation 339.5 kJ/mol
Molar heat capacity 23.35 J/(mol·K)
Vapour pressur
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1656 1807 1991 2223 2530 2942
Atomic properties
Oxidation states 6, 5, 4, 3, 2, 1, -1, -2 ​strongly acidic oxide
Electronegativity Pauling scale: 1.66
Ionisation energies
Atomic radius empirical: 128 pm
Covalent radius 139±5 pm
Color lines in a spectral range
Miscellanea
Creestal structurbody-centred cubic (bcc)
Body-centered cubic creestal structur for chromium
Speed o soond thin rod 5940 m/s (at 20 °C)
Thermal expansion 4.9 µm/(m·K) (at 25 °C)
Thermal conductivity 93.9 W/(m·K)
Electrical resistivity 125 n Ω·m (at 20 °C)
Magnetic orderin AFM (rather: SDW[1])
Young's modulus 279 GPa
Shear modulus 115 GPa
Bouk modulus 160 GPa
Poisson ratio 0.21
Mohs haurdness 8.5
Vickers haurdness 1060 MPa
Brinell haurdness 1120 MPa
CAS Nummer 7440-47-3
History
Diskivery Louis Nicolas Vauquelin (1797)
First isolation Louis Nicolas Vauquelin (1798)
Main isotopes o chromium
Iso­tope Abun­dance Hauf-life (t1/2) Decay mode Pro­duct
50Cr 4.345% >1.3×1018 y (β+β+) 50Ti
51Cr syn 27.7025 d ε 51V
γ -
52Cr 83.789% stable
53Cr 9.501% stable
54Cr 2.365% stable
Decay modes in parentheses are predictit, but hae nae yet been observed
| references | in Wikidata

Chromium is a chemical element whilk haes the seembol Cr an atomic nummer 24. It is the first element in Group 6. It is a steely-gray, lustrous, haurd an brickle metal[2] whilk taks a heich polish, resists tarnishin, an haes a heich meltin pynt. The name o the element is derived frae the Greek wird χρῶμα, chrōma, meanin colour,[3] acause mony o its compoonds is odious coloured.

Ferrochromium alloy is commercially produced frae chromite bi silicothermic or aluminothermic reactions an chromium metal bi roastin an leachin processes follaed bi reduction wi caurbon an then aluminium. Chromium metal is o heich vailyie for its heich corrosion resistance an haurdness. A major development in steel production wis the diskivery that steel coud be made heichly resistant tae corrosion an discolouration bi addin metallic chromium tae form stainless steel. Stainless steel an chrome platin (electroplatin wi chromium) thegither comprise 85% o the commercial uise.

Trivalent chromium (Cr(III)) ion is an essential nutrient in trace amoonts in humans for insulin, succar an lipid metabolism, awtho the issue is debatit.[4]

While chromium metal an Cr(III) ions are nae conseedert toxic, hexavalent chromium (Cr(VI)) is toxic an carcinogenic. Abandont chromium production steids eften require environmental cleanup.

References[eedit | eedit soorce]

  1. Fawcett, Eric (1988). "Spin-density-wave antiferromagnetism in chromium". Reviews of Modern Physics. 60: 209. Bibcode:1988RvMP...60..209F. doi:10.1103/RevModPhys.60.209. 
  2. Brandes, E. A.; Greenaway, H. T.; Stone, H. E. N. (1956). "Ductility in Chromium". Nature. 178 (587): 587. Bibcode:1956Natur.178..587B. doi:10.1038/178587a0. 
  3. χρῶμα, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
  4. "Chromium". Office of Dietary Supplements, US National Institutes of Health. 2016. Retrieved 26 June 2016.