Bent's rule states that more electronegative substituents prefer hybrid orbitals with more p-character, while lone pairs and less electronegative substituents occupy orbitals with more s-character. This explains subtle bond angle variations. In CH2F2, the F-C-F angle (108.3 degrees) is less than the H-C-H angle (113.7 degrees) because F prefers p-rich orbitals (smaller angle) while H bonds use s-rich orbitals (larger angle). In PF3Cl2, the more electronegative F atoms occupy axial positions (pure p-character in sp3d) while Cl atoms occupy equatorial positions (more s-character). This rule helps predict which positions substituents occupy in TBP and octahedral geometries.