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This question made me very discouraged. I have all the notion of OM for heteronucleated diatoms. I do not know if this is a really difficult question, or I do not know how to deal with it. Anyone have any idea how to build this diagram? or if you have any resolution with similar compound already would help a lot (links or books).

Problem
The phosphorus atom can generate compounds known as phosphines and phosphine oxides when reacted with molecular oxygen. An example of oxidized phosphine is phosphine oxide, the molecular formula of which is H 3 PO.
a) Mount the molecular orbitals diagram of phosphine oxide using Molecular Orbital Theory (TOM). Indicate in each connection in the diagram whether it is of type σ or type π.