In contrast to the slope in Figure , the predicted q is much lower in the case of the IS (first point in Figure ). The reason for this lower prediction is that in the IS the reacting proton does not exist as a single entity. Rather the charge is spread out over the hydronium ion (top right inset Figure ). This spreading out of the charge explains why the predicted q for a single proton is roughly 1 this approach, q IS→FS ≈ 0.6 -0.75 e, which is in line with Figure .