Oxides of phosphorus, arsenic, antimony, and bismuth
المؤلف:
Peter Atkins, Tina Overton, Jonathan Rourke, Mark Weller, and Fraser Armstrong
المصدر:
Shriver and Atkins Inorganic Chemistry ,5th E
الجزء والصفحة:
ص390-391
2025-09-08
489
Oxides of phosphorus, arsenic, antimony, and bismuth
Key points: The oxides of phosphorus include P4O6 and P4O10, both of which are cage compounds with Td symmetry; on progressing from arsenic to bismuth, the +5-oxidation state is more readily reduced to 3. Phosphorus forms phosphorus(V) oxide, P4O10, and phosphorus (III) oxide, P4O6. It is also possible to isolate the intermediate compositions having one, two, or three O atoms terminally attached to the P atoms. Both principal oxides can be hydrated to yield the corresponding acids, the P(V) oxide giving phosphoric acid, H3PO4, and the P(III) oxide giving phosphonic acid, H3PO3. As remarked in Section 4.5, phosphonic acid has one H atom attached directly to the P atom; it is therefore a diprotic acid and better represented as PHO(OH)2. In contrast to the high stability of phosphorus(V) oxide, arsenic, antimony, and bismuth more readily form oxides with oxidation number 3, specifically As2O3, Sb2O3, and Bi2O3. In the gas phase, the arsenic (III) and antimony (III) oxides have the molecular formula E4O6, with the same tetrahedral structure as P4O6. Arsenic, Sb, and Bi do form oxides with oxidation state +5, but Bi(V) oxide is unstable and has not been structurally characterized. This is another example of the consequences of the inert-pair effect. Note the coordination number of 6 for Sb and 4 for the lighter elements P and As, with their smaller atoms.
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