Pentachloride trivalent

The pyramidal structure of phosphorus trichloride, PCI3 typifies trivalent phosphorus compounds, while tetrahedral phosphoryl chloride, POCI3, the ions PCIJ and PO together with trigonal bipyramidal phosphorus pentachloride, PCI5, typify the spatial arrangements adopted by pentavalent phosphorus compounds. The hexachloro-phosphate (hexachlorophosphoride) anion. 

To maintain his doctrine Kekule also had to devise an artificial division of compounds into atomic compounds with the atoms held together by normal afSnities and molecular compounds composed of atomic ones combined by odd forces acting between molecules rather than between atoms. For example, Kekule classified sal-ammoniac (NH4CI) and phosphorus pentachloride (PCI5) as molecular compounds and assigned them the formulas NH3,HC1 and PCl3,Cl2 to preserve the trivalence of nitrogen and phosphorus. 

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