Curium electronic configuration

Symbol Cm atomic number 96 atomic weight 247 a radioactive transuranium actinide series element electron configuration [Rn]5/ 6di7s2 most stable valence state +3 most stable isotope Cm-247. Curium isotopes, half-hves and decay modes are ... 

Early in the actinide series, electrons in the 6d orbitals are lower in energy than there is 5f orbitals, This is clear from the ground-state electronic configurations (Table 9.3) of the atoms, which show that the 6d orbitals are filled before 5f. The 5f orbitals are starting to be filled at protoactinium, and with the exception of curium, the fid orbitals are not occupied again. 

Nobelium is a member of the actinide series of elements. The ground state electron configuration is assumed to be (Rn)5fl47s2, by analogy with the equivalent lanthanide element ytterbium ([Kr]4fl46s2) there has never been enough nobelium made to experimentally verify the electronic configuration. Unlike the other actinide elements and the lanthanide elements, nobelium is most stable in solution as the dipositive cation No ". Consequently its chemistry resembles that of the much less chemically stable dipositive lanthanide cations or the common chemistry of the alkaline earth elements. When oxidized to No, nobelium follows the well-estabhshed chemistry of the stable, tripositive rare earth elements and of the other tripositive actinide elements (e.g., americium and curium), see also Actinium Berkelium Einsteinium Fermium Lawrencium Mendele-vium Neptunium Plutonium Protactinium Ruthereordium Thorium Uranium. 

The following elements also have the same electronic configuration as actinium (i.e. 5s 5pl) in their outer-most electronic orbitals, while the inner 4d orbitals are being filled, on going from element to element. Neptunium, Plutonium, Americium, Curium, Berkelium... 

The superheavy elements are leading to deeper understanding of nuclear chemistry and the periodic table much as the lanthanides did at the start of the 20th century and the actinides did in mid-century. The favored +3 oxidation states of the lanthanides have electronic configurations 4f, 4f, 4f. .. 4f 4f 4f for the 14 consecutive lanthanides Ce through Lu respectively. These rare earths are chemically similar (and hard to separate) because their 4f orbitals exert little influence on reactivity. When Glenn T. Seaborg synthesized americium (95) and curium (96) in 1944, he discovered that, like the lanthanides, they readily form +3 oxidation states and fill 5f orbitals. In 1944, he proposed a new transi-... 

The electronic configurations 5f or 4f representing the half-filled f shells of curium and gadolinium, have special stability. Thus, tripositive curium and gadolinium, are especially stable. A consequence of this is that the next element in each case readily loses an extra electron through oxidation, so as to obtain the f structure, with the result that terbium and especially berkelium can be readily oxidized from the III to the IV oxidation state. Another manifestation of this is that europium (and to a lesser extent samarium) -just before gadolinium - tends to favor the 4f structure with a more stable than usual II oxidation state. Similarly, the stable f electronic configuration leads to a more stable than usual II oxidation state in ytterbium (and to a lesser extent in thuUum) just before lutetium (whose tripositive ion has the 4f structure). This leads to the prediction that element 102, the next to the last actinide element, will have an observable II oxidation state. 

A phenomenological model based on crystal structure, metallic radius, melting point, and enthalpy of sublimation has been used to arrive at the electronic configuration of berkelium metal [140]. An energy difference of 0.92 eV was calculated between the 5f 7s ground state and the 5f 6d 7s first excited state. The enthalpy of sublimation of trivalent Bk metal was calculated to be 2.99 eV (288 kJmol ), reflecting the fact that berkelium metal is more volatile than curium metal. It was also concluded that the metallic valence of the face-centered cubic form of berkelium metal is less than that of the double hexagonal close-packed modification [140]. 

Mochizuki and Okamoto applied the Dirac program for the estimation of stabilities of trivalent actinide elements and water or ammine complexes (Mochizuki and Okamoto 2002). Mochizuki and Tatewaki (2002) also carried out the electronic structure calculation on the hexa-hydrated ions of curium and gadolinium. They used the Dirac program and also predicted the fluorescence transition energy using the Complete Open-Shell Configuration Interaction (COSCI) method. Even the hexa-hydrate curium ion needs 2,108 basis functions for the fully relativistic four-component calculation. 

A simplistic picture of the situation is to have a relationship between the efifective moments of the f-element materials with the probable ion configuration. In this situation, localized f electrons in the metal would have the same moment as localized f electrons in a compound. The moment would depend on the number of such localized electrons regardless of the particular f-element s chemical form. Thus, the number of localized f electrons in Gd metal is seven (4f with three electrons in a ds conduction band), as it is in Cm metal (Sfconfiguration) there are also seven localized f electrons in both gadolinium and curium sesquioxides. Further, terbium and berkelium dioxides have seven localized f electrons. All six materials should have the same moment based on seven, unpaired free-ion electrons. 

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