Periodic Table/Fermium
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100Fm257 Da

Fermium

Actinide·Period 7·f-block

Radioactive metallic transuranic element, belongs to the actinoids. Ten known isotopes, most stable is Fm-257 with a half-life of 10 days. First identified by Albert Ghiorso and associates in the debris of the first hydrogen-bomb explosion in 1952.

Gallery

Fermium was first observed in the fallout from the Ivy Mike nuclear test.

U.S. Department of Energy, Public domain, via Wikimedia Commons

Bohr model of Fermium

Physical Propertiesmass · density · phase · crystal

Atomic Mass

257Da

Density

9.7000g/cm³

Phase (STP)

Solid

Melting Point

1800.2K

Boiling Point

—

Molar Heat

—

Crystal Structure

—

Atomic Radiiatomic · covalent · van der Waals

Atomic (Empirical)

—

Covalent

167.00pm

Van der Waals

245.00pm

Electronic Propertieselectronegativity · ionization · affinity

Electron Configuration

[Rn] 5f12 7s2

Electron Shells

2, 8, 18, 32, 30, 8, 2

Electronegativity

—

Electron Affinity

—

1st Ionization Energy

6.5kJ/mol

Oxidation States

+2, +3

Orbital DiagramAufbau · Hund's rule · Pauli exclusion

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

Full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 5f12 7s2Short: [Rn] 5f12 7s2

Ionization Energies (100 known)

1st6.5 kJ/mol2nd12.4 kJ/mol3rd23.2 kJ/mol4th39.3 kJ/mol5th55.0 kJ/mol6th74.0 kJ/mol7th93.0 kJ/mol8th120.0 kJ/mol9th136.0 kJ/mol10th162.0 kJ/mol11th185.0 kJ/mol12th209.0 kJ/mol13th237.0 kJ/mol14th257.0 kJ/mol15th276.0 kJ/mol16th300.0 kJ/mol17th326.0 kJ/mol18th351.0 kJ/mol19th377.0 kJ/mol20th402.0 kJ/mol21th430.0 kJ/mol22th453.0 kJ/mol23th616.0 kJ/mol24th647.0 kJ/mol25th680.0 kJ/mol26th716.0 kJ/mol27th749.0 kJ/mol28th782.0 kJ/mol29th837.0 kJ/mol30th871.0 kJ/mol31th909.0 kJ/mol32th944.0 kJ/mol33th1110.0 kJ/mol34th1150.0 kJ/mol35th1190.0 kJ/mol36th1230.0 kJ/mol37th1370.0 kJ/mol38th1420.0 kJ/mol39th1550.0 kJ/mol40th1600.0 kJ/mol41th1770.0 kJ/mol42th1850.0 kJ/mol43th1940.0 kJ/mol44th2030.0 kJ/mol45th2120.0 kJ/mol46th2210.0 kJ/mol47th2300.0 kJ/mol48th2390.0 kJ/mol49th2490.0 kJ/mol50th2590.0 kJ/mol51th2680.0 kJ/mol52th2760.0 kJ/mol53th2850.0 kJ/mol54th2950.0 kJ/mol55th3403.0 kJ/mol56th3480.0 kJ/mol57th3561.0 kJ/mol58th3647.0 kJ/mol59th3730.0 kJ/mol60th3810.0 kJ/mol61th3986.0 kJ/mol62th4070.0 kJ/mol63th4160.0 kJ/mol64th4245.0 kJ/mol65th4586.0 kJ/mol66th4670.0 kJ/mol67th4760.0 kJ/mol68th4840.0 kJ/mol69th5420.0 kJ/mol70th5510.0 kJ/mol71th5760.0 kJ/mol72th5860.0 kJ/mol73th9200.0 kJ/mol74th9370.0 kJ/mol75th9570.0 kJ/mol76th9770.0 kJ/mol77th9970.0 kJ/mol78th10160.0 kJ/mol79th10660.0 kJ/mol80th10860.0 kJ/mol81th11080.0 kJ/mol82th11280.0 kJ/mol83th11850.0 kJ/mol84th12020.0 kJ/mol85th12220.0 kJ/mol86th12390.0 kJ/mol87th14180.0 kJ/mol88th14400.0 kJ/mol89th14800.0 kJ/mol90th15000.0 kJ/mol91th30300.0 kJ/mol92th30800.0 kJ/mol93th31300.0 kJ/mol94th31800.0 kJ/mol95th38400.0 kJ/mol96th39100.0 kJ/mol97th40000.0 kJ/mol98th40482.2 kJ/mol99th158171.0 kJ/mol100th160808.0 kJ/molSuccessive Ionization Energies

Abundanceby mass

Biological Role

No biological role

Synthetic, radioactive element. No biological role.

Discovery

Discovered By

Argonne, Los Alamos, U of Calif

Named By

—

Year

1953

Nuclear Data

Known Isotopes

20

Stable Isotopes

0

Stable Mass Numbers

None

Isotopes of Fm20 known

NuclideZNMass (AMU)Half-lifeDecayJπAbundance
241Fm100141241.074311730 μsSF, α (0.14%), β⁺ (0.12%)5/2+—
242Fm100142242.073430800 μsSF (1%), α0+—
243Fm100143243.074414231 msα (0.91%), SF (0.09%), β⁺7/2-—
258Fm100158258.097077370 μsSF (1%), α0+—
259Fm100159259.1005961.50 sSF (1%)——
260Fm100160260.102809UnknownSF0+—

Click any isotope for its full page with decay chain:

241Fm242Fm243Fm244Fm245Fm246Fm247Fm248Fm249Fm250Fm251Fm252Fm253Fm254Fm255Fm256Fm257Fm258Fm259Fm260Fm
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