Ambiguity in oxidation state of phosphorus in H3PO3 [duplicate]








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[Oxidation number of phosphorus in phosphine](/questions/55477/oxidation-number-of-phosphorus-in-phosphine)

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Phosphorus(2.19) is less electronegative than hydrogen(2.20), so during calculation of oxidation state of phosphorus the oxidation state of hydrogen should be taken as-1 but in books it's taken as +1 why?




There are several electronegativity scales. In the Pauling scale, H and P are at 2.1. In the Mulliken scale, H is at 2.2 and P at 2.3. In the Allred and Rochow scale, it is the contrary : H is at 2.2 and P at 2.1. These scales are contradictory for H and P. So it is necessary to choose for teaching purposes. And book authors have usually chosen +1 for H, because H is rarely at -1, and only in very reactive compounds like NaH. 


Ref. : Michael O. Hurst, J. Chem. Ed. 79, June 2002. How we teach Molecular Structure to Freshmen. 


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