Pauling’s second rule

In garnet, Mg3Al2Si3012, an O2- ion is surrounded by 2 Mg2+, 1 Al3+ and 1 Si4+ particle. There are cation sites having coordination numbers of 4, 6 and 8. Use Pauling s second rule to decide which cations go in which sites. 

Silver cyanate, AgNCO, consists of infinite chains of alternating Ag+ and NCO- ions. Ag+ has c.n. 2 and only one of the terminal atoms of the cyanate group is part of the chain skeleton, being coordinated to 2 Ag+. Decide with the aid of Pauling s second rule which of the cyanate atoms (N or O) is the coordinated one. (Decompose the NCO- to N3-, C4+ and O2-). 

The coordination of an O2- ion is three Al3+ ions within an A1404 cube and one Mg2+ ion outside of this cube. This way it fulfills the electrostatic valence rule (Pauling s second rule, cf p. 58), i.e. the sum of the electrostatic bond strengths of the cations corresponds exactly to the charge on an O2- ion ... 

The experimental uncertainties in the measured bond lengths ensure that the sum of experimental bond valences around any particular ion will never exactly equal the atomic valence and, as shown in later chapters, there are cases where this discrepancy gives important information about the crystal chemistry, but the valence sum rule, which states that the sum of experimental bond valences around each atom is equal to the atomic valence (F, in eqn (3.3)), is much better obeyed than Pauling s second rule. 

Applying Pauling s second rule to the surface of goethite (see Figure 2.19), position protons on the surface oxygen atoms to create a chaige-balanced structure. 

In 1929 Pauling proposed as the second of his Principles Determining the Structures of Complex Ionic Crystals [1], that a cation-anion bond could be characterized by the oxidation state (atomic valence) of its cation divided by its coordination number. He showed that the total amount of this quantity, usually now called the Pauling Bond Strength, received by the anion was approximately equal to the anion oxidation state. He called this the Electrostatic Valence Principle, but it is now commonly referred to as Pauling s Second Rule. 

This determination of the coordination number of the ion is predicated on the electrical neutrality principle given earlier (see page 19). This principle is also called the electrostatic valence principle and is part of Pauling s second rule In a stable ionic structure the valence of each anion, with changed sign, is exactly or nearly equal to the sum of the strengths of the electrostatic bonds to it from the adjacent cations. (Pauling, 1960)... 

A simple but powerful explanation of the fact that bonds exclusively to 0(5) and not 0(2), may be that the electrostatic bond strength sums (Pauling s second rule) of 0(5) and 0(2) are +1.5 and +1.75, respectively . These values are smaller than the formally required +2.0. Such low values are the reason for the deficiency in positive charge around the conduction plane clearly 0(5) is more negatively charged than 0(2) and is more likely to attract D ". 

Fuertes A (2006) Prediction of anion distributions using pauling s second rule. Inorg Chem 45 9640... 

Pauling s second rule states that the value of the first for acids of the formula... 

Pauling s second rule states that the sum of individual electrostatic bond strengths (e.b.s.) around a particular ion are equal in magnitude to the ion charge, i.e., that local electroneutraUty is observed. The e.b.s. for a cation surrounded by nX " is given by ... 

Pauling s second rule relates acid strength to the number of non-hydrogenated oxygen atoms in the molecule. The more of these there are, the stronger is the acid. The first acid dissociation constant, is predicted to be of the order of 10 mol litre where t is the number of terminal (non-hydrogenated) oxygens in the acid. 

Use Pauling s second rule to predict how the acidity of the highest oxoacid of an element varies across the fourth Period, from Group IV to Group VII. 

Use Pauling s second rule to predict (approximately) the first dissociation constant of an acid, from a consideration of the value of t in the general formula AOXOH) . (Questions 11.4-11.7 and 12.2)... 

According to Pauling s second rule, the acid strength is expected to increase in the direction... 

The acid of stoichiometry H3PO3 (phosphorous acid) has a first dissociation constant typical of a moderately weak acid that is r = 1. According to Pauling s second rule, the dissociation constant for an acid with t = 0 would be expected to be around 10 mol litre which suggests that H3PO3 is not the hydroxy acid P(OH)3, but contains one P=0 group. The correct structure for this compound Q.22. 

From Pauling s second rule we can say that, as H2SO4 has two terminal oxygen atoms (t = 2), it should be a strong acid. 

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