Huckel transformation theory is applied to the study of the hybridization problem in ground state NH3. Under assumptions similar to those recently introduced for H2O, minimization of the model Huckel energy at the valence level yields a trigonometric relation between bond angle and hybridization parameter showing that hybridization opens the interbond angle beyond 90 degrees. A further orthogonal transformation mixing in AOs belonging to A(1) and E symmetry yields four orthogonal sp(3) hybrids of C-3v symmetry on nitrogen that can be engaged in the axially symmetric lone pair and three equivalent straight N-H bonds making the experimental interbond angle. (C) 2009 Elsevier B. V. All rights reserved.