Chromium

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Chromium
24Cr
-

Cr

Mo
vanadiumchromiummanganese
Appearance
sillery metallic
General properties
Name, seembol, nummer chromium, Cr, 24
Pronunciation /ˈkrmiəm/ KROH-mee-əm
Element category transeetion metal
Group, period, block 6, 4, d
Staundart atomic wicht 51.9961(6)
Electron confeeguration [Ar] 3d5 4s1
2, 8, 13, 1
Electron shells of chromium (2, 8, 13, 1)
History
Discovery Louis Nicolas Vauquelin (1797)
First isolation Louis Nicolas Vauquelin (1798)
Physical properties
Phase solid
Density (near r.t.) 7.19 g·cm−3
Liquid density at m.p. 6.3 g·cm−3
Meltin pynt 2180 K, 1907 °C, 3465 °F
Boilin pynt 2944 K, 2671 °C, 4840 °F
Heat o fusion 21.0 kJ·mol−1
Heat o vaporization 339.5 kJ·mol−1
Molar heat capacity 23.35 J·mol−1·K−1
Vapor pressure
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 1.66 (Pauling scale)
Ionization energies
(more)
1st: 652.9 kJ·mol−1
2nt: 1590.6 kJ·mol−1
3rd: 2987 kJ·mol−1
Atomic radius 128 pm
Covalent radius 139±5 pm
Miscellanea
Crystal structure body-centered cubic
Chromium has a body-centered cubic crystal structure
Magnetic orderin AFM (rather: SDW[1])
Electrical resistivity (20 °C) 125 nΩ·m
Thermal conductivity 93.9 W·m−1·K−1
Thermal expansion (25 °C) 4.9 µm·m−1·K−1
Speed of sound (thin rod) (20 °C) 5940 m·s−1
Young's modulus 279 GPa
Shear modulus 115 GPa
Bulk modulus 160 GPa
Poisson ratio 0.21
Mohs hairdness 8.5
Vickers hairdness 1060 MPa
Brinell hairdness 1120 MPa
CAS registry nummer 7440-47-3
Most stable isotopes
Main article: Isotopes o chromium
iso NA hauf-life DM DE (MeV) DP
50Cr 4.345% >1.3×1018 y (β+β+) 1.167 50Ti
51Cr syn 27.7025 d ε - 51V
γ 0.320 -
52Cr 83.789% 52Cr is stable wi 28 neutrons
53Cr 9.501% 53Cr is stable wi 29 neutrons
54Cr 2.365% 54Cr is stable wi 30 neutrons
Decay modes in parentheses are predictit, but hae nae yet been observed
· r

Chromium is a chemical element which haes the seembol Cr an atomic nummer 24. It is the first element in Group 6. It is a steely-gray, lustrous, haird an brittle metal[2] which taks a heich polish, resists tarnishin, an has 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 are intensely coloured.

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