II and Other Gillespie-unstable Systems

In aqueous solution, N is low and most frequently 3. The amphoteric dissolution of Pb(OH)2 in excess of OH- is now known to produce Pb(OH)J, an interesting contrast to Be(0H)4 2 formed by a much smaller central atom. The moderately soluble PbCl2 and Pbl2 are known to dissolve in an excess of Cl- to PbClJ or of 1 to PblJ. It is not certain whether PbClJ binds additional chloride ligands the absorption spectrum of Pb(II) shifts marginally143 as a function of the concentration of strong HC1. 

Crystal structures containing the s2 type cations are sometimes cubic of types such as NaCl, K2PtCl6 and SrTi03 withN = 6 and in other cases highly distorted. 

Electric Dipolar Polarizability and the Approximately Additive Molar Refract ivities 

Whereas the hard-hard interactions in Pearson s Dual Rule essentially are Coulombic, the soft-soft interactions frequently invite the comment that they represent polarizability. This word has connotations for the chemists which are not very different 

In the visible and ultra-violet region of frequencies v (the wave-number a is t /c) the electric dipolar polarizability a is connected with a summation over all the k excited states to which the transition has the oscillator strength P  

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