Atomic Theory

Xx                                                       Al  – 3e-        Al3+                                                             

X                                                       loses three electrons                                                          

The atom of the aluminium loses its outermost three electrons and therefore no longer remains neutral (it no longer has an equal number of protons and electrons). It then contains more protons (positively charged particles) than electrons and therefore becomes a tripositively charged ion – Al3+.  It could also be called a trivalent cation.

The electrons lost by the aluminium could in turn be gained by another atom which needs to gain electrons to get a stable outer electronic configuration. An oxygen atom having an atomic number of 8 and therefore an electronic configuration of (2 6) could, for example, gain these electrons.