White elemental phosphorus consists of tetrahedral P4 molecules and is an important sou...

White elemental phosphorus consists of tetrahedral P₄ molecules and is an important source of phosphorus for synthesis. In contrast, tetrahedral As₄ (yellow arsenic) is unstable, and decomposes to a grey As allotrope with a sheet structure. However, AsP₃ , previously only observed at high temperature in the gas phase, has been isolated at ambient temperature as a white solid, where an As atom replaces one vertex of the tetrahedron.

a. The Raman spectrum of AsP₃ , shown next, exhibits four absorptions. Is this consistent with the proposed structure? (Facile Synthesis of AsP₃, Brandi M. Cossairt, Mariam- Céline Diawara, Christopher C. Cummins. © 2009. The American Association for the Advancement of Science. Reprinted with permission from AAAS.)

b. If As₂P₂ is ever isolated as a pure substance, how many Raman absorptions would be expected? (Reference: B. M. Cossairt, C. C. Cummins, J. Am. Chem. Soc. 2009 , 131 , 15501.)

c. Could a pure sample of P₄ be distinguished from pure AsP₃ simply on the basis of the number of Raman absorptions? Explain.