Metals usually form cations because they like to lose electrons to get a full octet. Nonmetals usually form anions because they like to gain electrons to get a full octet.
Aluminum will lose 3 electrons to form a cation Beryllium will lose 2 electrons to form a cation Copper can lose either 1 or 2 electrons to form a cation. Silicon can gain 4 electrons to form an anion.
