The basicity decreases when one goes down the group in a periodic table with the elements, because of the increasing size of the atoms on going down the group. Explanation: ... And thereby the metallic character of the atom increases and thence the basicity decreases.

Does basicity increase down a group?

In general, basicity increases down a group (e.g., in the alkaline earth oxides, BeO < MgO < CaO < SrO < BaO). Acidity increases with increasing oxidation number of the element.

Why does basicity increase going up a group?

Weaker bases have negative charges on more electronegative atoms; stronger bases have negative charges on less electronegative atoms. ... This is best illustrated with the haloacids and halides: basicity, like electronegativity, increases as we move up the column.