Aluminum typically loses three electrons when it forms an ion, resulting in a +3 charge. This is because aluminum has three valence electrons in its outer shell. To achieve a stable electronic configuration, aluminum tends to lose these three electrons. By doing so, it attains the electron arrangement of the nearest noble gas, neon, which has a full outer shell of electrons.
The loss of electrons is a common behavior for metals, and since aluminum is a metal, this tendency is clearly observed in its ionic formation. When aluminum loses these electrons, it becomes positively charged, forming an aluminum ion (Al3+).