[en] A quasielastic scattering scaling law for the most probable energy loss has been derived for ion-molecule scattering, and verified for Ne⁺ and Ne⁰ on H₂, D₂ in the small-angle, low-keV energy range. This scaling is shown to break down for the more fundamental collision D⁺+H₂. The neon and D⁺ results portray the importance of the valence forces in scattering, and shows a breakdown of the concept of a two-center potential for ion-molecule scattering. A single electronically inelastic channel is found for this collision. The inelastic excitation of H₂ by D⁺, in the same energy and angular range, is reported to yield a sharp universal reduced cross-section plot, similar to the He⁺+H₂ collision. This supports the existence of a quasimolecule that is formed during close encounters of the collision. No strong direct dissociation of the target H₂ molecule is found