Core electrons oxidation numbers

In larger structures, the number of equivalent units becomes huge. In the docosanuclear dendrimer made of an Os(II)-based core and 21 Ru(II)-based units, a one-electron oxidation process, assigned to the Os(II)-based unit, is followed by a 12-electron process, due to the simultaneous oxidation of the 12 equivalent and non-interacting peripheral Ru(II)-based units [36]. 

The report of the first zinc compound with a Zn-Zn core elicited a number of critical comments on the structure and bonding of decamethyldizincocene, and the interpretation of the results.236,237 None of the authors of these commentaries questioned the data or their interpretation. Parkin, however, has pointed out that the formal oxidation state of +1 for zinc in this compound is merely due to the convention that metals are assigned an oxidation state of 0 when they form bonds with like atoms.237 If the conventional definition of valence, namely the capacity of atoms to form bonds to other atoms is used, then the zinc atoms in decamethyldizincocene are not monovalent, but divalent. The synthesis of a paramagnetic organozinc compound in which zinc uses only one of its two 4s electrons will remain an interesting challenge to many synthetic organometallic chemists. 

There are a number of Ni111 complexes with macrocyclic nitrogen ligands. They are usually made by one-electron oxidation of the Ni11 species the ring size and size of cavity in the macrocycles has an influence on the Nin/Niin redox potential. Some Ni111 macrocycles can also be oxidized to NiIv. A structurally characterized example of a Nim macrocycle is the deep purple complex (17-G-XV) which contains a square-planar NiN4 core.12... 

A is correct. Since chromium forms more than one oxidation state and aluminum forms only one, chromium requires the variability in number of bonds formed. This means choices C and D are out. Chromium has electrons in the orbitals of the 2p subshell, but these are core electrons and not used for making bonds. Chromium has 6 valence electrons, 5 of which are in the orbitals of the 3d subshell. 

ChemProp Group Oxidation Number - Inert Gas Core - 8-electron configuration - V-type Diagrams - Group Oxidation State - Variable Valence. Ligands - [M(OH2)6] - Oxyanions. 

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