Americium
actinideProperties
| Property | Value |
|---|---|
| Atomic Mass | 243 amu |
| Category | actinide |
| Period | 7 |
| Electron Configuration | [Rn] 5f7 7s2 |
| Electronegativity | 1.3 (Pauling) |
| Oxidation States | 6, 5, 4, 3 |
| Melting Point | 1449 K (1175.8 °C) |
| Boiling Point | 2880 K (2606.8 °C) |
| Density | 12 g/cm³ |
| Discovered By | Glenn T. Seaborg, Ralph A. James, Leon O. Morgan, Albert Ghiorso (1944) |
About Americium
Americium is the transuranium element you have probably owned without knowing it. Every ionization smoke detector hides a roughly 1-microcurie disc of Am-241 sandwiched between gold and silver foil — its 5.486 MeV alphas keep a small chamber of air weakly conducting, and a smoke particle is enough to disrupt the current. That single application moved more grams of synthetic actinide into civilian hands than any other use in history. The isotope itself is a fission-product byproduct: Pu-241 in spent reactor fuel beta-decays to Am-241 with a 14.4-year half-life, which is why aged plutonium gets steadily more gamma-active and harder to work with in a glovebox. Am-241's own 432.2-year half-life makes it convenient for long-life calibration sources and Am-Be neutron generators used in oil-well logging tools dropped down boreholes. The chemistry leans on the +3 state in solution, which behaves enough like Eu3+ that europium is the standard non-radioactive stand-in when developing separation chemistry for partitioning and transmutation schemes that aim to burn americium out of high-level waste.
Fun Fact
Curium-244 wasn't named until after americium was, but Seaborg's team actually identified it first — they kept Am hidden under the codename pandemonium and Cm under delirium because the chemistry was so painful to pin down.
Common Uses
- Am-241 alpha source in residential ionization smoke detectors
- Am-Be neutron sources for oil-well porosity logging tools
- Gamma calibration standards at 59.5 keV for HPGe detectors
- Density and thickness gauges for paper, glass, and steel sheet
- Reference target for partitioning research on minor actinide separation