Electron formulae

Actually the halides all do have the formula BX3, and show no tendency to associate, while the simplest hydride, B2H6, has not begun to dissociate into 2BH3 at a temperature at which it begins to lose hydrogen. If BH3 were given an electronic formula with an electron-pair bond between boron and each H... 

Lewis s theory and Heitler and London s extension permitted the reasonably certain attribution of specific electronic formulas to a great many compounds. In other cases, however, it was possible to set up a number of alternative electronic formulas for a molecule or crystal, and often no sound argument could be advanced supporting any one of them against the others. For example, Lewis gave the perchlorate ion the... 

For each molecule, ion, or free radical that has only localized electrons, it is possible to draw an electronic formula, called a Lewis structure, that shows the location of these electrons. Only the valence electrons are shown. Valence electrons may be found in covalent bonds connecting two atoms or they may be unshared. The student must be able to draw these structures correctly, since the position of electrons changes in the course of a reaction, and it is necessary to know where the electrons are initially before one can follow where they are going. To this end, the following rules operate ... 

Substitution of a dash by two electrons yields the electronic formula... 

There will be a large resonance energy that gives an appreciable contribution to the stability of the molecule. The situation is different in two molecules that probably are stabilized by resonance, as well, e.g. NaO and X3H. For the first, three electronic formulae with complete octets can be wTritten... 

Simple algebraic equations for calculating the number of shared electrons for structures with completed octets and other completed electron shells were given by I. Langmuir (J.A.C.S. 41, 868 [1919]. These equations usually need not be called upon, since electronic formulas of the sort desired can be written easily with a little practice. 

If we remove two vertex boron atoms, the resulting framework is an arachno (Gr., spider s web ) structure. With two vertices missing, the structure is even more open than is the nido case and the resemblance to the parent closo structure is less appurent. Arachno structures obey the electronic formula 2n + 6 (or n + 3 electron pairs). Pentaborane(l I), BjB,. must therefore have an arachno structure. In the arachno series the extra hydrogen atoms form ertdo B—H bonds (lying dose to (he framework) as well as bridges. 

The hypho (Gr.. net ) series of boranes, with electronic formula 2n + 8, has beer suggested to augment the closo, nido, and arachno series. Although no neutral boranes fit this scheme, some borane derivatives do. It is also passible to construct units consisting of more than one of the above types. These are called cmjuncio (Latin, joined subunits ) structures. 

Another type of formula often written for compounds is the electronic formula, showing the distribution of the valence electrons among the atoms of the molecule, as shown in Fig. 5 and explained under valence and molecule. 

For the special case of two equivalent electrons formula (20.1) turns into (9.1). 

As it stands, this is not acceptable, because it implies that the central hydrogen atom accommodates four electrons, which would breach the Pauli principle. However, a valency-bond interpretation of this (rather weak) hydrogen bond is possible, by the alternative electronic formulae (1) and (2). They imply some electron delocalization, and hence enhanced stability via hydrogen-bonding energy, in the sense that a truer formula than (1) alone is a combination of (1) and (2). 

In conformity with the accepted notation for simplified electronic formulae, the structural formula of nitric acid according to Sugden is... 

Constitution.—The formulae must, on account of the properties of pyrophosphoric acid and its relation to orthophosphoric acid, show the phosphorus atoms as saturated. This can be done either by the electronic formulae or by those containing quinquevalent phosphorus, since as already shown the two kinds of formulae are interchangeable. The molecule may be (1) symmetrical or (2) unsymmetrical —... 

Now this multiplicity of the electron configuration occurs not only in the bonding between two atoms but also in many cases in which one can compose for the whole molecule more than one electron formula, which thus represent different electron configurations. 

Write electronic formulas for calcium peroxide, CaOg, and zirconium dioxide, ZrOo. Write equations for the reactions of these two substances with sulfuric acid. 

The process of the completion of the electronic shell is repeated as lor ihc second period elements and is shown by the electronic formulae ... 

From scandium to vau.idivim, atomic number 23, dierc occurs a further filling of the 3 orbitals and hence die electronic formula of vanadium b... 

With die next element, chromium, however, it appears that for the first time in the construction of the periodic classification an element does not retain the electronic configuration of the previous atom. Thus in the atom of cliromium diere is only one 4s electron and five 3[Pg.28]

After the completion of the 4/state, the 5first element in this series being hafnium with the electronic formula... 

The CNN diazo linkage has a linear geometry. The electronic formula is described by resonance structures, the most important of which are... 

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