The Use or Not of d Orbitals by Nonmetals

Theoretical Arguments against d Orbital Participation in Nonmetals 

Several workers have objected to the inclusion of d orbitals in bonding in nonmetals. The principal objection is to the large promotion energy required to effect 

20 These same general arguments apply to alt of the heavier nonmetals. The d and/orbitals are heavily shielded by the more penetrating s and p electrons. 

The second alternative is the thrcc-ccnter. Ibur-elcctron hand developed by simple molecular orbital theory lor the noble gas lluoridcs t ree Chapter 17). Since this predicts that each bonding pair of electrons leach bond ) is spread over three nuclei. Ihe bond between two or the nuclei is less than that of a normal two-center, two-electron bond. Furthermore, since the nonbonding pair of electrons is localized on the fluorine atoms, there is a separation of charge ( ionic character ). In both respects, then, this interpretation agrees with Pauling s approach and with the experimental facts. 

In the case of nitrogen, experimental work indicates that pentacooidinatc-1 and 

Two alternatives have been suggested to account for the higher oxidation States of the noninetals both reduce the importance of high-encigy d orbitaLs. Pauling has. suggested that resonance of the following type could take place  

The ckxiblc bonil rule ctin be simcd iis fdlows dements having a principal quantum number greater than two are not likely lo Tonn Pn-Pv bonds. 

18J The 3 f oifailal Jisiritnuion imaions in d conliguraiions lAJ in ihe D term of P (s li d B) in the D term of S V). Line lefiicsenis a typcal S—F bond length. IMolilicd from Mitchell. K. A. R. Chan. Krr. IMP. 6P, 1ST. Reproduced with permission.  

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First- and Second-Row Anomalies 858 The Use of p Orbitals in Pi Bonding 861 The Use (or Not) of d Orbitals by Nonmetals 86ft Reactivity and d Orbital Participation 875... 

In general, the octet rule works for representative metals (Groups lA, IIA) and nonmetals, but not for the transition, inner-transition or post-transition elements. These elements seek additional stability by having filled half-filled or filled orbitals d or/subshell orbitals. The octet rale does not, however, accurately predict the electron configurations of all molecules and compounds. Not all nonmetals, nor metals, can form compounds that satisfy the octet rale. As a result, the octet rale must be used with caution when predicting the electron configurations of molecules and compounds. For example, some atoms violate the octet rale and are surrounded with more than four electron pairs. 

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