fermium

Physical properties

Fermium is the eighth transuranic element in the actinide series of group 14 (IVA) of theperiodic table. Similar to einsteinium, fermium was produced and discovered in the debrisresulting from the explosion of the nuclear hydrogen bomb in 1952. Its existence was keptsecret because of security measures that were established during World War II, thus keepingAlbert Ghiorso and his colleagues at the University of California at Berkeley from receivingcredit for the discovery until 1955. Fermium’s melting point is thought to be about1500+degrees Celsius, but its boiling point and density are unknown since so little of it isproduced and because of the short half-lives of its isotopes.

Isotopes

There are a total of 21 isotopes of fermium. Their half-lives range from fermium-258’s 370 microseconds to fermium-257’s 100.5 days, which is the longest of allits isotopes. None of fermium’s isotopes exist in nature. All are artificially produced andare radioactive.

Origin of Name

Named after and to honor the scientist Enrico Fermi.

Occurrence

Fermium does not exist in nature. All of it is artificially produced in cyclotrons, isotopeparticle accelerators, or nuclear reactors by a very complicated decay process involving six stepsof nuclear bombardment followed by the decay of beta particles, as follows:1. Plutonium-239 (plus 2 neutrons) to ₉₄Pu-241 → americium-241+ β-.2. Americium-241 (plus 1 neutron) to ₉₅Am-242 → to curium-242 + β-.3. Curium-242 (plus 7 neutrons) to ₉₆Cm-249 → to berkelium-249 + β-.4. Berkelium-249 (plus 7 neutrons) to ₉₇Bk-250 → to californium-250 + β-.5. Califorium-250 (plus 3 neutrons) to ₉₈Ca-253 → to einsteinium-253 + β-.6. Einstenium-253 (plus 1 neutron) to ₉₉Es-254 → to fermium-254 + β-.

Characteristics

The chemical characteristics of fermium are not very well known, but they are similarto its homologue erbium, the rare-earth element located just above it in the lanthanideseries.
The nuclear reaction in the hydrogen bomb that produced fermium was the result of theacquisition of 17 neutrons by uranium from the explosion resulting in uranium-255 and somegamma radiation. U-255 decays by β-electron emission to form fermium-255, as depicted inthe equation as follows: ₉₂U-238 + 17 neutrons and gamma radiation → ₉₂U-255 → ₁₀₀Fm-255 + the emission of 8 electrons.

History

Fermium, the eighth transuranium element of the actinide series to be discovered, was identified by Ghiorso and co-workers in 1952 in the debris from a thermonuclear explosion in the Pacific in work involving the University of California Radiation Laboratory, the Argonne National Laboratory, and the Los Alamos Scientific Laboratory. The isotope produced was the 20-hour ²⁵⁵Fm. During 1953 and early 1954, while discovery of elements 99 and 100 was withheld from publication for security reasons, a group from the Nobel Institute of Physics in Stockholm bombarded ²³⁸U with 16O ions, and isolated a 30-min α-emitter, which they ascribed to 250100, without claiming discovery of the element. This isotope has since been identified positively, and the 30-min half-life confirmed. The chemical properties of fermium have been studied solely with tracer amounts, and in normal aqueous media only the (III) oxidation state appears to exist. The isotope ²⁵⁴Fm and heavier isotopes can be produced by intense neutron irradiation of lower elements such as plutonium by a process of successive neutron capture interspersed with beta decays until these mass numbers and atomic numbers are reached. Twenty isotopes and isomers of fermium are known to exist. 257Fm, with a half-life of about 100.5 days, is the longest lived. ²⁵⁰Fm, with a half-life of 30 min, has been shown to be a product of decay of Element ²⁵⁴102. It was by chemical identification of ²⁵⁰Fm that production of Element 102 (nobelium) was confirmed. Fermium would probably have chemical properties resembling erbium.

Uses

Because such small amounts of fermium are produced and because the half-lives of its isotopesare so short, there are no commercial uses for it except for basic scientific research.

Uses

Tracer studies.

Definition

A radioactive transuranic element of the actinoid series, not found naturally on Earth. It is produced in very small quantities by bombarding ²³⁹Pu with neutrons to give ²⁵³Fm (half-life 3 days). Several other short-lived isotopes have been synthesized. Symbol: Fm; p.n. 100; most stable isotope ²⁵⁷Fm (half-life 100.5 days).

Definition

fermium: Symbol Fm. A radioactivemetallic transuranic element belongingto the actinoids; a.n. 100; massnumber of the most stable isotope257 (half-life 10 days). Ten isotopesare known. The element was firstidentified by A. Ghiorso and associatesin debris from the first hydrogen-bomb explosion in 1952. It isnamed after Enrico Fermi.

Definition

Element 100, aw 254, valence of 3, half-life 3 h. A synthetic radioactive element with atomic number 100 discovered in 1952. Fermium has since been prepared in a nuclear reactor by irradiating californium, plutonium, or einsteinium with neutrons in a cycl

Hazard

All the radioisotopes of fermium are dangerous radiation hazards. There is little chance ofcoming in contact with one of fermium’s isotopes given that they all have very short half-livesand do not exist for long periods. In addition, very small amounts are produced and mainlyavailable for research purposes.