Aluminium has 13 electrons, arranged 1s2 2s2 2p6 3s2 3p1. Written on the previous noble gas that is [Ne] 3s2 3p1, and the shells hold 2, 8, 3 electrons from the innermost outwards.
Hund's rule leaves 1 unpaired electron in the ground state, which is what makes the free atom paramagnetic.
The periodic table, read every way a chemistry course asks for. This tool needs JavaScript; these are the pages it offers: