Americium is a synthetic, silvery radioactive actinide. The isotope Am-241 is an alpha-emitter widely used in ionization-type smoke detectors; higher isotopes (e.g., Am-243) are research materials in the actinide series.
Americium (Am) is an actinide element with atomic number 95, located in period 7 of the f-block, between plutonium (Pu) and curium (Cm). It is synthetic—not found in significant natural quantities—and was first produced in nuclear reactors.
\(^{241}\mathrm{Am}\) is a convenient alpha emitter with a half-life of about 432 years. In ionization smoke detectors, its alpha particles ionize air in a small chamber, creating a tiny current. Smoke particles disrupt this ionization, reducing the current and triggering the alarm.
Its decay can be summarized as:
\(^{241}\mathrm{Am} \;\xrightarrow{\alpha}\; ^{237}\mathrm{Np} + \alpha + \gamma\)
Americium is typically made by neutron capture on plutonium isotopes in a reactor, followed by beta decays. A simplified pathway to \(^{241}\mathrm{Am}\) is:
\(^{239}\mathrm{Pu}(n,\gamma)\,^{240}\mathrm{Pu}(n,\gamma)\,^{241}\mathrm{Pu} \xrightarrow{\beta^-} \, ^{241}\mathrm{Am}\)
Other isotopes like \(^{243}\mathrm{Am}\) arise via additional captures and decays.
Americium commonly exhibits +3 (dominant in water) and can access +4, +5, and +6 under suitable conditions. The Am(III) aqua ion is typically written as \(\mathrm{[Am(H_2O)_9]^{3+}}\), and higher states may form americyl dioxo cations analogous to uranyl/plutonyl:
A commonly cited ground-state configuration is [Rn] 5f7 7s2. A half-filled 5f7 subshell contributes to characteristic magnetic properties and influences the stability of the +3 oxidation state in aqueous chemistry.
Yes. Many Am isotopes are alpha emitters (with accompanying gamma from daughters). The main hazards are internal exposure (inhalation/ingestion of particulates) and chemical toxicity as a heavy metal. Safe handling requires licensed facilities, glove boxes or hot cells, HEPA-filtered ventilation, contamination monitoring, dosimetry, and compliant waste management. Consumer smoke detectors contain very small sealed sources engineered for safety when intact.
Representative compounds include:
Americium isotopes (notably \(^{241}\mathrm{Am}\) and \(^{243}\mathrm{Am}\)) contribute to the long-term radiotoxicity of spent nuclear fuel. Research explores partitioning and transmutation strategies in advanced reactors to reduce long-lived minor actinides by converting them to shorter-lived nuclides.
Two illustrative relations are:
\(^{241}\mathrm{Am} \;\to\; ^{237}\mathrm{Np} + \alpha\)
\(^{243}\mathrm{Am}(n,\gamma)\,^{244}\mathrm{Am}\)