That makes those nuclei heavier still, converting them into neptunium, plutonium, americium and curium.All these by-products of nuclear fission are radioactive, and many will remain so for thousands—sometimes millions of years.
Those that do not, such as technetium and americium, have been substituted, respectively, by rhenium and neodymium, which have similar traits.
Metallic californium has been prepared and is structurally similar to metallic americium, curium, berkelium, and most lanthanoid metals.
The other new elements discovered by Seaborg were americium (95), curium (96), berkelium (97), californium (98), einsteinium (99), fermium (100), mendelevium (101), nobelium (102), and seaborgium (106).
Beginning with americium, however, the electron energy levels seem to be sufficiently separated so that mixing does not occur.
The +4 actinoids thorium, protactinium, uranium, neptunium, plutonium, berkelium, and, to a lesser extent, americium, curium, and californium are sufficiently stable to undergo chemical reactions in aqueous solutions.
The Soviets may have synthesized a few atoms of element 105 in 1967 at the Joint Institute for Nuclear Research in Dubna, Russia, U.S.S.R., by bombarding americium-243 with neon-22 ions, producing isotopes of element 105 having mass numbers of 260 and 261 and half-lives of 0.1 second and 3 seconds, respectively.
Three other transuranium isotopes plutonium-238, amerisotopes plutonium-238nium-252—have demonstrated substantial practicandapplicalifornium-252 have
The isotope americium-241 is the most important because of its availability.
When mixed with beryllium, it generates neutrons at the rate of 1.0 × 107 neutrons per second per gram of americium-241.
Some detectors contain slivers of americium-241; the isotope's constant emission of radiation creates a chemical process that screens for smoke.
