Why does Al have a larger atomic radius than B

Explanation:

While atomic radii DECREASE across a Period, a row of the Period Table, from left to right as we face the Table, atomic radii INCREASE down a Group, a column of the Periodic Table, due to the shielding of the valence electrons by the closed valence shell(s) that intervenes between the nucleus and the valence, outermost electrons.

pie chart because it is in percents ( % )