Quick answerAmericium (Am) is an actinide with atomic number 95 and a mass number of 243 (the most stable isotope), in period 7. It was discovered by Seaborg, James, Morgan, and Ghiorso in 1944. It is used for smoke detectors and industrial gauges. Its electron configuration is [Rn] 5f7 7s2.
Americium is the element inside nearly every household smoke detector, silently watching for fire with a speck of radioactivity.
Key facts
| Symbol | Am |
|---|---|
| Atomic number | 95 |
| Atomic mass | [243] — mass number of the most stable isotope |
| Category | actinide |
| Group | — (f-block element, no group number) |
| Period | 7 |
| Block | f-block |
| Electron configuration | [Rn] 5f7 7s2 |
| Discovered | Seaborg, James, Morgan, and Ghiorso, 1944 |
| Uses | smoke detectors, industrial gauges, neutron sources, research, spacecraft power |
Quick quiz
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Keep exploring
- Periodic table — all 118 elements
- Thorium (Th) — another actinide, atomic number 90
- Protactinium (Pa) — another actinide, atomic number 91
- Uranium (U) — another actinide, atomic number 92
- Neptunium (Np) — another actinide, atomic number 93
- Plutonium (Pu) — another actinide, atomic number 94
- Curium (Cm) — another actinide, atomic number 96
- Berkelium (Bk) — another actinide, atomic number 97
- Californium (Cf) — another actinide, atomic number 98
- Einsteinium (Es) — another actinide, atomic number 99
- Fermium (Fm) — another actinide, atomic number 100
- All actinide elements — on the periodic table
Sources & last updated
- CIAAW — Standard Atomic Weights
- PubChem Periodic Table
- Wikipedia — Timeline of chemical element discoveries
Last updated: . Figures are shown with their year; where sources disagree, the value is left out rather than estimated.