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100 Fm Fermium [257]

Actinide

Fermium 镄

[Rn] 5f¹² 7s²

  • Period 7
  • Group —
  • Block f
  • Solid

Electron configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹² 6s² 6p⁶ 7s²

Orbital diagram (valence)

5f ↑↓↑↓↑↓↑↓↑↓↑↑
7s ↑↓
Electrons per shell
2, 8, 18, 32, 30, 8, 2
Unpaired electrons
2
Zeff (Slater)
2.85

Properties

Atomic weight
[257]
Electronegativity (Pauling)
1.3
First ionization energy
627.2 kJ/mol
Electron affinity
no data
Covalent radius
no data
van der Waals radius
no data
Melting point
1800 K
Boiling point
no data
Density
no data
Melting / boiling point
1526.8 °C / —
Common oxidation states
+3
Discovered
1952

Brackets give the mass number of the longest-lived isotope

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/molLa: 538.1 kJ/molCe: 534.4 kJ/molPr: 527.2 kJ/molNd: 533.1 kJ/molPm: 535.5 kJ/molSm: 544.6 kJ/molEu: 547.1 kJ/molGd: 593.4 kJ/molTb: 565.8 kJ/molDy: 573 kJ/molHo: 581 kJ/molEr: 589.3 kJ/molTm: 596.7 kJ/molYb: 603.4 kJ/molLu: 523.5 kJ/molHf: 658.5 kJ/molTa: 761.3 kJ/molW: 770 kJ/molRe: 760.3 kJ/molOs: 839.4 kJ/molIr: 878 kJ/molPt: 868.4 kJ/molAu: 890.2 kJ/molHg: 1007 kJ/molTl: 589.3 kJ/molPb: 715.6 kJ/molBi: 703.3 kJ/molPo: 812.1 kJ/molAt: 916.6 kJ/molRn: 1037 kJ/molFr: 376.3 kJ/molRa: 509.3 kJ/molAc: 498.8 kJ/molTh: 586.6 kJ/molPa: 568.3 kJ/molU: 597.6 kJ/molNp: 604.6 kJ/molPu: 584.7 kJ/molAm: 578.2 kJ/molCm: 580.8 kJ/molBk: 601.1 kJ/molCf: 607.9 kJ/molEs: 619.4 kJ/molFm: 627.2 kJ/molMd: 634.9 kJ/molNo: 641.6 kJ/mol 0102030405060708090100110Atomic number Z05001000150020002500First ionization energy / kJ/mol

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