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24 Cr Chromium 51.996

Transition metal

Chromium 铬

[Ar] 3d⁵ 4s¹

  • Period 4
  • Group 6
  • Block d
  • Solid

Electron configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s¹

Orbital diagram (valence)

3d ↑↑↑↑↑
4s ↑
Electrons per shell
2, 8, 13, 1
Unpaired electrons
6
Zeff (Slater)
2.95

Properties

Atomic weight
51.996
Electronegativity (Pauling)
1.66
First ionization energy
652.9 kJ/mol
Electron affinity
64.26 kJ/mol
Covalent radius
139 pm
van der Waals radius
189 pm
Melting point
2180 K
Boiling point
2944 K
Density
7.15 g/cm³
Melting / boiling point
1906.8 °C / 2670.8 °C
Common oxidation states
+6, +3, +2
Discovered
1797

Natural isotopes

Mass number AAbundance
50Cr4.35 %
52Cr83.79 %
53Cr9.50 %
54Cr2.37 %

Isotope masses: AME2020; abundances: IUPAC/CIAAW representative values.

Chromium in the course

The lessons that discuss this element most (ranked by mentions).

Lab experiments with Chromium

Standard reduction potentials

CrX2OX7X2−(aq)+14 HX+(aq)+6 eX−→2 CrX3+(aq)+7 HX2O(l)\ce{Cr2O7^2-(aq)} + \ce{14H+(aq)} + \ce{6e-} \mathrel{\ce{->}} \ce{2Cr^3+(aq)} + \ce{7H2O(l)}+1.360 V
CrOX4X2−(aq)+4 HX2O(l)+3 eX−→Cr(OH)X3(s)+5 OHX−(aq)\ce{CrO4^2-(aq)} + \ce{4H2O(l)} + \ce{3e-} \mathrel{\ce{->}} \ce{Cr(OH)3(s)} + \ce{5OH-(aq)}−0.130 V
CrX3+(aq)+eX−→CrX2+(aq)\ce{Cr^3+(aq)} + \ce{e-} \mathrel{\ce{->}} \ce{Cr^2+(aq)}−0.407 V
CrX3+(aq)+3 eX−→Cr(s)\ce{Cr^3+(aq)} + \ce{3e-} \mathrel{\ce{->}} \ce{Cr(s)}−0.744 V
CrX2+(aq)+2 eX−→Cr(s)\ce{Cr^2+(aq)} + \ce{2e-} \mathrel{\ce{->}} \ce{Cr(s)}−0.913 V
All potentials

Periodic trend

H: 1312 kJ/molHe: 2372 kJ/molLi: 520.2 kJ/molBe: 899.5 kJ/molB: 800.6 kJ/molC: 1086 kJ/molN: 1402 kJ/molO: 1314 kJ/molF: 1681 kJ/molNe: 2081 kJ/molNa: 495.8 kJ/molMg: 737.7 kJ/molAl: 577.6 kJ/molSi: 786.5 kJ/molP: 1012 kJ/molS: 999.6 kJ/molCl: 1251 kJ/molAr: 1521 kJ/molK: 418.8 kJ/molCa: 589.8 kJ/molSc: 633 kJ/molTi: 658.8 kJ/molV: 650.9 kJ/molCr: 652.9 kJ/molMn: 717.3 kJ/molFe: 762.4 kJ/molCo: 760.4 kJ/molNi: 737.1 kJ/molCu: 745.4 kJ/molZn: 906.4 kJ/molGa: 578.8 kJ/molGe: 762.2 kJ/molAs: 947 kJ/molSe: 940.9 kJ/molBr: 1140 kJ/molKr: 1351 kJ/molRb: 403 kJ/molSr: 549.5 kJ/molY: 599.8 kJ/molZr: 640.1 kJ/molNb: 652.1 kJ/molMo: 684.3 kJ/molTc: 702.4 kJ/molRu: 710.2 kJ/molRh: 719.7 kJ/molPd: 804.4 kJ/molAg: 731 kJ/molCd: 867.8 kJ/molIn: 558.3 kJ/molSn: 708.6 kJ/molSb: 833.6 kJ/molTe: 869.3 kJ/molI: 1008 kJ/molXe: 1170 kJ/molCs: 375.7 kJ/molBa: 502.9 kJ/mol 0510152025303540455055Atomic number Z05001000150020002500First ionization energy / kJ/mol

Group 6

Data: PubChem periodic table (public domain); atomic weights are IUPAC abridged standard values; covalent radii from Cordero et al. (2008).