This research is a continuation of two previously published papers with the aim of studying and finding a general lone pair orbital description in molecules. In this paper, Delocalized Floating Spherical Gaussian Orbital (DFSGO) has been used, while original FSGO, which is localized, was used in the two previous papers (Parts I and II, J. Mol. Struct. (Theochem), 236 (1991) 85 and J. Mol. Struct. (Theochem), 288 (1993) 29, respectively). The procedure has some advantages over both FSGO and SCF methods. Therefore, the descriptions of molecular orbitals are determined by the irreducible representations by the SCF procedure, and cannot be subjective. Many models have been used and tested in order to obtain, simultaneously, correct bond lengths and bond angles. The proposed models for lone pair have been tested for three molecules: CH 2 (singlet) and the ground states of NH 3 and H 2 O. The lone pair description contains contributions from axial p-type plus two concentric gaussians, and two nonaxial concentric gaussians (positive and negative), which are situated on each of the interatomic distances. In this way relatively correct bond lengths and bond angles are predicted with lower percentages of error in comparison with those of Part II of this series: 2.112 Da and 101.970 o for CH 2 ; 1.914 Da and 106.582 o for NH 3 ; 1.810 Da and 104.303 o for H 2 O.