Rule of eight

The rule of 12 replaces the rule of eight as the guiding principle of Lewis-like dot diagrams. 

Rule of eights Approximate the interval between doses (in hours) by multiplying the serum creatinine level (mg/dL) by 8. For example, a patient weighing 60 kg with a serum creatinine level of 2 mg/dL could be given 60 mg (1 mg/kg) every 16 hours (2 x 8). 

The wave mechanics contains in it the Lewis concepts of atomic structure, of the rule of eight, of the rule of two, and of the valence property of the unpaired electron. How these atoms can be combined to form the molecules of Chapter I with their localized bonds, geometrical arrangements, and free or restricted rotations, etc., will be taken up in the following chapter. 

Lewis assumed that the pair of electrons was one of the stable arrangements, so that apart from the formation of noble gas electron arrangements, atoms having unpaired electrons would form bonds. This he calls the rule of two, to distinguish it from the rule of eight. Both rules are explicit in his theory. 

The rule of eight may replace the old rules of valence to predict the modes of combination of the elements, more especially for those... 

In many cases double bonds shown in the older formulas must be replaced by single bonds in electron structures to maintain the rule of eight. Thus an amine oxide is represented by the formula... 

The species PF5, PFg, SFg are exceptions to the octet rule. In PF5 there are ten electrons in the valency group around the phosphorus atom in PF and SFg there are twelve electrons in the valency groups. The elements in the first row, on the other hand, are bound rigidly to the rule of eight. ... 

As Moeller observed in the 1950s [106], Although the octet rule is definitely a useful concept, its applications are limited and it should not receive the universal attention normally focussed upon it. It is much more important that attention be directed to the important phenomenon of electron pairing. The concept that the electrons seek to pair with each other is nearly universal in application and is always useful as a first approximation in predicting chemical behaviour. This rule of two is far more fundamental than the rule of eight . To contemporary sensibilities, this seems a bit harsh and generally multicentred, and dative bonds which favour adherence to the octet rule represent a convenient starting point for discussion. 

Describe, use, or explain each of the following with respect to forming a covalent bond electron cloud, charge cloud, or charge density valence electrons half-filled electron orbital filled electron orbital electron sharing orbital overlap octet rule or rule of eight. 

These and many similar observations lead us to believe that the stability of a noble-gas electron configuration is the result of a minimization of energy associated with that configuration. This generalization is known as the octet rule, or rule of eight, because each atom has completed its octet. The tendency toward a complete octet of electrons in a bonded atom reflects the natural tendency of a system to move to the lowest energy state possible. 

One of the most powerful tools available to the chemist is the electronic theory of valence. Still it is not yet being used generally to full advantage. The two principal factors responsible for the delay seem to be reluctance to abandon the rule of eight and failure to make use of the concept of atomic orbitals. 

Ever since the proposal of the theory of the covalent bond by G. N. Lewis in 1916, it has been obvious that there are numerous compounds which do not obey the rule of eight, which was strongly emphasized by Kossel and Langmuir. However, elementary textbooks have stressed it so thoroughly that the rule of eight is still generally accepted by those unfamiliar with the recent literature in the field. 

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