The New Element Americium (Atomic Number 95)

Pressure-Induced Spectroscopic Changes in a Californium 1D Material Are Twice as Large as Found in the Holmium Analog

“…For example, a large unit-cell volume expansion occurs between plutonium and americium metal that corresponds to the localization of 5 f electrons later in the series. − Likewise, as cations within coordination complexes and compounds, elements past plutonium possess inherently stable 3+ oxidation states similar to that of lanthanides as exemplified by CfCl 3 , [An­(H 2 O) 9 ]­(CF 3 SO 3 ) 3 (An = U – Cm, Cf), and Am 2 (C 2 O 4 ) 3 (H 2 O) 6 ·4H 2 O . This historic observation played a substantial role in the placement of the actinide series below the lanthanides in the periodic table in the 1940s, − although, it should be noted that both Langmuir and Bohr, , using newly realized quantum mechanical principles, were the first to identify the proper placement of actinides two decades before americium was first prepared …”

“…6 This historic observation played a substantial role in the placement of the actinide series below the lanthanides in the periodic table in the 1940s, 7−9 although, it should be noted that both Langmuir and Bohr, 10,11 using newly realized quantum mechanical principles, were the first to identify the proper placement of actinides two decades before americium was first prepared. 7 More recently, a second break in the actinide series that starts at californium has been identified in both the metallic state and in compounds. 12−15 For example, when californium is prepared as a pure element in the form of a thin film it displays the properties of a divalent metal.…”

Pronounced Pressure Dependence of Electronic Transitions for Americium Compared to Isomorphous Neodymium and Samarium Mellitates

“…1,4 Therefore, it was hypothesized that elements 95 and 96 would behave more like lanthanides, and this resulted in the first identification of americium and curium in late 1944. 5,6 Americium is one of the last elements in the periodic table that is present in large quantities in nuclear waste. Each year in a typical 1000-MWe-pressurized water reactor, approximately 3.81 kg of americium is generated, with an additional 9 kg of americium generated from plutonium-241 decay over the following years.…”

The unveiled states of americium

“…In the autumn of 1944 this observation was the first confirmed sighting of element 95 (ref. 2). Further experiments produced other isotopes, of which the 243 95 isotope was found to be the most stable.…”