americium-241

chemical isotope

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June 18, 2026

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Americium (Am) is a synthetic chemical element with atomic number 95, belonging to the actinoid series. It was first produced in 1944 from plutonium and named after the United States.1

The most significant isotope is americium-241, which is produced in nuclear reactors. This isotope is used in smoke detectors due to its alpha-particle emission and in various gauges utilizing its gamma radiation. All americium isotopes are radioactive, with americium-243 being the most stable due to its longer half-life of 7,370 years, compared to americium-241's 433 years.1

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transuranium element
Practical applications of transuranium isotopes
Three other transuranium isotopes—plutonium-238, americium-241, and californium-252—have demonstrated substantial practical applications. One gram of plutonium-238 produces approximately 0.57 watt of thermal power, primarily from alpha-particle decay, and this property has been used in space exploration to provide energy for small thermoelectric-power units.
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Three other transuranium isotopes—plutonium-238, americium-241, and californium-252—have demonstrated substantial practical applications. One gram of plutonium-238 produces approximately 0.57 watt of thermal power, primarily from alpha-particle decay, and this property has been used in space exploration to provide energy for small thermoelectric-power units.
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americium
…nature, americium (as the isotope americium-241) was artificially produced from plutonium-239 (atomic number 94) in 1944 by American chemists Glenn T. Seaborg, Ralph A. James, Leon O. Morgan, and Albert Ghiorso in a nuclear reactor. It was the fourth transuranium element to be discovered (curium, atomic number 96, was discovered…
Read More
…nature, americium (as the isotope americium-241) was artificially produced from plutonium-239 (atomic number 94) in 1944 by American chemists Glenn T. Seaborg, Ralph A. James, Leon O. Morgan, and Albert Ghiorso in a nuclear reactor. It was the fourth transuranium element to be discovered (curium, atomic number 96, was discovered…
Read More