Inelastic scattering cross sections to individual bound excited states of 104Sn were measured at 150 MeV/u beam energy and analyzed to evaluate the contribution of neutron and proton collectivity. State-of-the-art Quasi-Particle Random Phase Approximation (QRPA) with the D1M Gogny interaction reproduces the experimental proton collectivity and our inelastic scattering cross sections once used as input for a reaction calculation together with the Jeukenne–Lejeune–Mahaux (JLM) potentials. Experimental inelastic scattering cross section decreases by 40(24)% from 112Sn to 104Sn. The present work shows that (i) proton and neutron collectivities are proportional over a large range of tin isotopes (including 104Sn), as is typical for isoscalar excitations, and (ii) the neutron collectivity dominates. It suggests that the plateau in the mass range displayed by E2 transition probabilities is driven by neutron collectivity.