Chromium

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Chromium,  24Cr
Chromium crystals and 1cm3 cube.jpg
General properties
Appearancesillery metallic
Staundart atomic wecht (Ar, staundart)51.9961(6)[1]
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
Groupgroup 6
Periodperiod 4
Element category  transition metal
Blockd-block
Electron confeeguration[Ar] 3d5 4s1
Electrons per shell
2, 8, 13, 1
Pheesical properties
Phase (at STP)solit
Meltin pynt2180 K ​(1907 °C, ​3465 °F)
Bylin pynt2944 K ​(2671 °C, ​4840 °F)
Density (near r.t.)7.19 g/cm3
when liquid (at m.p.)6.3 g/cm3
Heat o fusion21.0 kJ/mol
Heat o vapourisation339.5 kJ/mol
Molar heat capacity23.35 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 states6, 5, 4, 3, 2, 1, -1, -2 ​strongly acidic oxide
ElectronegativityPauling scale: 1.66
Ionisation energies
Atomic radiusempirical: 128 pm
Covalent radius139±5 pm
Coloyr lines in a spectral range
Spectral lines o Chromium
Miscellanea
Creestal structurbody-centred cubic (bcc)
Body-centered cubic creestal structur for chromium
Speed o soond thin rod5940 m/s (at 20 °C)
Thermal expansion4.9 µm/(m·K) (at 25 °C)
Thermal conductivity93.9 W/(m·K)
Electrical resistivity125 n Ω·m (at 20 °C)
Magnetic orderinAFM (rather: SDW[2])
Young's modulus279 GPa
Shear modulus115 GPa
Bouk modulus160 GPa
Poisson ratio0.21
Mohs haurdness8.5
Vickers haurdness1060 MPa
Brinell haurdness1120 MPa
CAS Nummer7440-47-3
History
DiskiveryLouis Nicolas Vauquelin (1797)
First isolationLouis 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[3] 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,[4] 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.[5]

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. Meija, J.; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305. 
  2. 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. 
  3. 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. 
  4. χρῶμα, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
  5. "Chromium". Office of Dietary Supplements, US National Institutes of Health. 2016. Retrieved 26 June 2016.