Aside from the presence of the second proton, the general form and nodal structure of the 2a, density distribution in the water molecule is remarkably similar to the 2o distributions in CH and HF, and particularly to the latter. The charge density accumulated on the bonded side of the oxygen nucleus in the 2a, orbital is localized near this nucleus as the corresponding charge increase in the 2o orbital of HF is localized near the fluorine. The charge density of the 2a, molecular orbital accumulated in the region between the three nuclei will exert a force drawing all three nuclei together. The 2a, orbital is a binding orbital Although the three 2p atomic orbitals are degenerate in the oxygen atom the presence of the two protons results in each 2p orbital experiencing a different potential field in the water molecule. the nonequivalence of the 2 p orbitals in the water molecule is evidenced by all three possessing different symmetry properties The three 2p orbitals will interact to different extents with the protons and their energies will differ The 2px orbital interacts most strongly with the protons and forms an orbital of b2 symmetry by overlapping with the(1s,-1s2) combination of 1 s orbitals on the hydrogens. The charge density contours for the Ib2 orbital indicate that this simple LCAO description accounts for the principal features of this molecular orbital. The lb2 orbital concentrates charge density along each O-H bond axis and draws the nuclei together. The charge density of the 1b2 orbital binds all three nuclei. In terms of the forces exerted on the nuclei the 2a, and Ib2 molecular orbitals are about equally effective in binding the protons in the water moleculeAside from the presence of the second proton, the general form and nodal structure of the 2a1 density distribution in the water molecule is remarkably similar to the 2s distributions in CH and HF, and particularly to the latter. The charge density accumulated on the bonded side of the oxygen nucleus in the 2a1 orbital is localized near this nucleus as the corresponding charge increase in the 2s orbital of HF is localized near the fluorine. The charge density of the 2a1 molecular orbital accumulated in the region between the three nuclei will exert a force drawing all three nuclei together. The 2a1 orbital is a binding orbital. Although the three 2p atomic orbitals are degenerate in the oxygen atom the presence of the two protons results in each 2p orbital experiencing a different potential field in the water molecule. The nonequivalence of the 2p orbitals in the water molecule is evidenced by all three possessing different symmetry properties. The three 2p orbitals will interact to different extents with the protons and their energies will differ. The 2px orbital interacts most strongly with the protons and forms an orbital of b2 symmetry by overlapping with the (1s1 - 1s2 ) combination of 1s orbitals on the hydrogens. The charge density contours for the lb2 orbital indicate that this simple LCAO description accounts for the principal features of this molecular orbital. The lb2 orbital concentrates charge density along each O-H bond axis and draws the nuclei together. The charge density of the 1b2 orbital binds all three nuclei. In terms of the forces exerted on the nuclei the 2a1 and lb2 molecular orbitals are about equally effective in binding the protons in the water molecule