Which oxide is more basic, MgO or BaO? Why?

Explanation

BaO, because basic character of oxides increases down the group. On going down the group, the size of the cation increases and hence its acidic nature becomes less. As a result those with smaller sizes generally become amphoteric or more acidic. MgO is a basic oxide too but BaO with a larger sized `Ba^(+2)` ion has greater basic nature. This can also be proven by looking at the strength of the hydroxide bases. Where `Ba(OH)_2` is a strong base, `Mg(OH)_2` is a weak base and poorly soluble in water also.