I understand the acidity of a substance increases with electronegativity and size (valence shell space) of an atom (periodic trend) that contains a hydrogen atom (Brønsted-Lowry). However when looking at following pairs, I am not able to determine which one is a stronger acid.
$$\ce{H3O+ ,\ H2O}$$
Further, I would want to reason, the relationship between the charge and acidity/ basicity.
