Explanation:
On a periodic table, the atomic size is depicted by the radius of the atom.
Across a period, the atomic radius reduces progressively from left to right.
Down the group from top to bottom, atomic radii increases progressively.
For the ionization energy, from left to right, across the period, it increases progressively and down a group it reduces.
These two trends are related in that as the atomic radius decreases across the period there is an increasing nuclear charge which is not compensated for by the the successive shells of electrons being added. This also similar down the group.
