Question

Water, after turning into hydronium ion,still has one lone pair electron left.So, can it pair with one more H+ ion?If no, why?

Answer 1

Explanation:

Hydronium ions form in an effort to delocalize charge. if there is excess H+ in an aqeuos solution, then you will have proximity between H2O and H+. H+ is a very localized positive charge. H2O in proximity has two electron groups extending out into the space around it. The two extra electron groups of two electrons each combined with the two bound hydrogens in H2O make a tetra shape (kind of like a triangular pyramid with the points being the direction of the electron groups) So due to the electromagnetic forces involved it is a lower energy state (and therefore preferred/more stable) for the H+ to associate with one of these electron groups instead of being free floating, which makes for less localization of the positive charge. Or to put it another way, because molecular thermodynamics says so.