Here's why:

* Electron Configuration: Aluminum's electron configuration ends in 3p1. The 'p' in 3p1 signifies that its outermost electron resides in a p orbital. Elements with their last electron in a p orbital are part of the p-block.

* Location: Aluminum is found in Group 13 (also known as Group IIIA) and Period 3 of the periodic table. This entire group falls within the p-block.