Fermium is a synthetic, highly radioactive actinide metal (element 100). It was first identified in 1952 in the debris of the Ivy Mike hydrogen bomb test. Only microgram quantities have ever been produced; chemistry indicates predominant +3 and also +2 oxidation states.
Fermium (Fm) is a man-made actinide with atomic number 100. It was first identified in 1952 in fallout from the Ivy Mike thermonuclear test, where extreme neutron fluxes created very heavy actinides that were later isolated by radiochemical techniques. The element is named after Enrico Fermi.
Fermium lies in the f-block (actinide series), period 7, between einsteinium (Es) and mendelevium (Md). It is distinctive for being available only in microgram or smaller amounts, for its intense radioactivity, and for showing mainly the +3 oxidation state (with accessible +2 under strong reducing conditions).
Several isotopes exist; laboratory work often uses Fm-257 (half-life on the order of \(10^2\) days), which primarily decays by alpha emission with some spontaneous fission. Shorter-lived isotopes like Fm-255 (hours) are also produced in experiments, limiting the time window for measurements.
Fermium forms via multiple neutron captures and subsequent beta decays on lighter actinides (e.g., uranium, plutonium, curium, californium) under extremely high neutron flux, then is separated radiochemically. A stylized segment is:
\(\cdots \xrightarrow{(n,\gamma)} \mathrm{Es} \;\xrightarrow{\beta^-}\; \mathrm{Fm}\)
Practical production requires high-flux reactors and complex, multi-stage solvent-extraction/ion-exchange separations.
A commonly cited ground-state configuration is [Rn] 5f12 7s2. In solution, Fm(III) dominates (trivalent actinide chemistry). Under strongly reducing conditions, Fm(II) can be stabilized, which is useful for separations from neighboring trivalent actinides.
Because of minuscule amounts, compounds are studied at tracer levels. Representative forms include Fm(III) in halides and oxides (e.g., Fm2O3 in analogy), and coordination complexes of Fm(III) with oxygen-donor ligands (nitrates, phosphates, carbonates). Fm(II) species can be generated in highly reducing media.
Outside of research, no routine applications exist due to scarcity, cost, and radioactivity. Fermium is valuable for advancing actinide chemistry, nuclear data, and understanding of 5f-electron bonding and redox trends across the late actinides.
Yes. Fermium is a radiotoxic heavy metal. Primary risks are internal exposure (inhalation/ingestion of particulates) and radiation from alpha decay (plus daughters and possible gammas). Handling requires licensed hot-cell or glove-box facilities, HEPA filtration, remote tools, dosimetry, shielding, and compliant waste management.
A representative decay for a long-lived isotope is alpha decay:
\(^{257}\mathrm{Fm} \;\to\; ^{253}\mathrm{Cf} + \alpha\)
Some isotopes also undergo spontaneous fission, producing fission fragments and multiple neutrons.
Radiochemists exploit subtle differences in oxidation state and complex formation. For example, selective reduction to Fm(II) followed by ion-exchange or solvent extraction can help separate fermium from trivalent neighbors like einsteinium or mendelevium. Careful control of acid concentration and ligand choice tunes separation factors.