In p-block, when we move from left to right in a period, the acidic character of the oxides increases due to increase in electronegativity. For example,
In 2nd period B2O3 < CO2 < N2O3 (acidic nature increases).
In 3rd period A12O3 < SiO2 < P4O10 < SO3 < C12O7 (acidic character increases).
On moving down the group, acidic character decreases and basic character increases, e.g.,
Among the oxides of same element, higher the oxidation state of the element, stronger is the acid. For example, SO3 is a stronger acid than SO2.
B2O3 is weakly acidic and on dissolution in water, it forms orthoboric acid. Orthoboric acid does not act as a protonic acid (it does not ionise) but acts as a weak Lewis acid.