.The pho~phoryl bond is presented as a. resonan~e hybrid between singly and triply bound structures. The types of electromcally excited states and a number of their potential surfaces can be understood within the confines of a singly bound model: However, a detailed analysis of the electronic distribution within the ground state shows significant contribution from the tnpl~ bound structure. In fact, increasing the electronegativity of the ligands at phosphorus increases the contribution of t~e tnp~y bound structure, so that the. PO bond order approaches that of a double bond. The thiophosphoryl bond may be VIewed m much the same manner but IS rather weaker and contains less multiple bond character than does the PO group.