The concept of 3dπ orbital bonding in molecules of second row atoms is tested by making some model calculations on phosphoryl molecules, X3PO. Values of exponents for 3s, 3p, and 3d orbitals of phosphorus have been calculated in an electrostatic calculation where X is F, Cl, C, and H. For F3PO, estimates have also been made on the effect of interatomic exchange. The main conclusion for F3PO is that the molecular environment strongly contracts the 3d orbitals at phosphorus with π symmetry with respect to the P—O bond, thereby indicating the feasibility of double bond interactions with oxygen 2pπ orbitals.