The Molecular Orbital Theory of Chemical Valency. V. The Structure of Water and Similar Molecules

J. A. Pople
1950 Proceedings of the Royal Society A  
The theory of m olecular an d equivalent o rbitals developed in previous p ap ers o f th is series is used to discuss th e spatial distrib u tio n of lone-pair electrons in molecules such as H 20 an d N H 8 an d th e p a rt th e y p la y in determ ining th e equilibrium configuration. Previous trea tm e n ts o f H aO have assum ed th a t th e lone pairs are essentially u n altered b y m olecular form ation. I t is show n here, on th e other han d , th a t th e y will be displaced so as to be m
more » ... aced so as to be m ainly concentrated on th e side of th e O -nucleus rem ote from th e hydrogen atom s. A n im p o rta n t consequence of th is is th a t th e lone-pair electrons will m ake a co n trib u tio n to th e to ta l dipole m om ent. Com parison of th e experim entally observed m om ent w ith a n ap p ro x im ate q u a n ti ta tiv e tre a tm e n t suggests th a t, as a result of this, tran sfe r o f electrons from th e hydrogen atom s to th e oxygen does n o t occur to th e e x te n t th a t h as previously been believed. The v ariatio n of th e sp atial d istrib u tio n of th e orbitals of H aO w ith changes o f nuclear configuration is exam ined a n d it is show n th a t, in th e equilibrium position, th e electronic stru ctu re can be described approxim ately b y tw o sets o f tw o eq u iv alen t o rb itals p o in tin g in n early te trah ed ra l directions. T he dependence of to ta l energy on bo n d angle is discussed an d i t is show n th a t electrostatic repulsions betw een th e eq u iv alen t o rb itals are m a jo r factors in determ ining th e equilibrium configuration. Sim ilar considerations ap p ly to N H 3. I n t r o d u c t i o n [ 323 ] 22-2
doi:10.1098/rspa.1950.0103 fatcat:gbccufc7lnaixjy7ynnvn3yy5i