Basic Information

Fermium Home

Basic Information

Isotopes of Fermium

Mr. Rushin's online Period Table

Reference Page

Element Name Fermium

Element Symbol

Atomic Number 100
Atomic Mass (257) amu
Group Rare Earth Metal, Actinoid
Standard State Presumably a solid at 257 K
Number of Neutrons 157
Melting Point 1527 *C
Boiling Point Unknown
Density in Natural State Unknown
Natural Abundance 0%
Electron Configuration (Rn)5f127s2

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Fermium is a man-made element, discovered in the residues of a thermonuclear explosion in 1952.  The element was identified by Ghiorso and his co-workers.  In 1955 the element was named Fermium in honor of the nuclear physicist Enrico Fermi The explosion took place in the Pacific Ocean during experiments involving the University of California Radiation Laboratory, Argonne National Laboratory, and Los Alamos Scientific Laboratory.  The isotope that was produced from this explosion was 255Fm.  During this time, 1953 to 1954, the discovery of the elements 99 and 100 were not published for security reasons.

During this period, a group of scientist from the Nobel Institute of Physics in Stockholm further researched the element to confirm its existence.  They took a 238U and bombarded it with 160 ions, forming a alpha-emitting element, with a 30 minute half-life.  Since that time, this alpha-emitter has been verified as an isotope of Fermium.  

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The element is believed to have an oxidation state of +3, therefore the ion would be Fm3+.  If this is true then the compounds Fermium chloride, FmCl3, and Fermium oxide, Fm2O3, can be formed.  The equations for these two are:

  • Fm3+ + 3Cl- FmCl3

  • 2Fm3+ + 3O2- Fm2O3

(Exploring Chemical Elements and their Compounds)