Lithium atom, electron distribution

Lithium (atomic number 3), 3Li, has three electrons to distribute among the subshells. Following the first arrow in the filling diagram, two electrons are added to the ls-orbital, filling it completely. The next higher arrow leads to the 2s-subshell. The third electron is placed in the 2s-orbital in the 2s-subshell. The configuration of lithium would be read as one-s-two, two-s-one. ... 

An electron configuration of an atom is a particular distribution of electrons among available subshells. The notation for a configuration lists the subshell symbols, one after the othCT, with a supCTscript giving the number of electrons in that subsheU. For example, a configuration of the lithium atom (atomic number 3) with two electrons in the Is subsheU and one electron in the 2s subshell is written ls 2s. ... 

Together with the concept of loge, Daudel and his group introduced in the literature the notion of "densite electronique differentielle" and applied it initially to the lithium molecule (Roux and Daudel 1955). The differential electronic density was defined as the difference between the electronic density computed at a point of a molecule and the density that existed at the same point if the atoms were side by side without interacting. This notion revealed the effect of the chemical bond on the electronic distribution density (Daudel, Brion, and Odiot 1955 Roirx, Besnainou, and Daudel 1956). A positive difference meant that in the formation of the molecule, there was a region where there was a higher electronic interaction than when the atoms did... 

Since the first structure determination by Wadsley [56] in 1952 there has been confusion about the correct cell dimensions and symmetry of natural as well of synthetic lithiophorite. Wadsley determined a monoclinic cell (for details see Table 3) with a disordered distribution of the lithium and aluminium atoms at their respective sites. Giovanoli et al. [75] found, in a sample of synthetic lithiophorite, that the unique monoclinic b-axis of Wadsley s cell setting has to tripled for correct indexing of the electron diffraction patterns. Additionally, they concluded that the lithium and aluminum atoms occupy different sites and show an ordered arrangement within the layers. Thus, the resulting formula given by Giovanelli et al. 

The same principles that are valid for the surface of crystalline substances hold for the surface of amorphous solids. Crystals can be of the purely ionic type, e.g., NaF, or of the purely covalent type, e.g., diamond. Most substances, however, are somewhere in between these extremes [even in lithium fluoride, a slight tendency towards bond formation between cations and anions has been shown by precise determinations of the electron density distribution (/)]. Mostly, amorphous solids are found with predominantly covalent bonds. As with liquids, there is usually some close-range ordering of the atoms similar to the ordering in the corresponding crystalline structures. Obviously, this is caused by the tendency of the atoms to retain their normal electron configuration, such as the sp hybridization of silicon in silica. Here, too, transitions from crystalline to amorphous do occur. The microcrystalline forms of carbon which are structurally descended from graphite are an example. 

Similar conclusions are reached for the distribution of electron density in the isomeric adduct 101, where the carbon atoms adjacent to the reaction center are shifted upheld with respect to the corresponding 1,4-dihydropyridazine. Somewhat higher shielding is found for the C-5 atom (8.0 ppm) than for C-3 (3.7 ppm), but in either position the electron density appears to be appreciably lower than for C-4 in adduct 100. Such differences are presumably to be related to the nature of the lithium-nitrogen bond, but clearly to a hrst approximation all the adducts from diazines and phenyllithium can be described as undissociated species, whether that bond is ionized or strongly polar covalent. 

Cyclopentadienyllithium. The tt charge in the aromatic cyclopentadienyl anion is distributed equally to all five carbon atoms. A lithium counterion should thus electrostatically favor a central location (Csv, 26a) over the tt face. The same conclusion is reached on the basis of MO considerations (46). The six interstitial electron interactions involving the three cyclopentadienyl TT orbitals and those of corresponding symmetry on lithium (one of these is shown in 26b) also favor structure 26a. 

Let us consider the derivation of the electron configuration of the elements from lithium to neon which constitute the second period of Men el eff s classification. The distribution of the electrons in the ground positions of the atoms is given below. In the atom of lithium, the first two electrons occupy the u position, the third electron according to the Pauli principle must fall into the electron shell having the main quantum number equal to two. The electron accordingly occupies the position of minimum energy within this shell, which is the 2s orbital. 

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