Covalent bonding is a bond between two nonmetals and the difference in electronegativity is between 0 and 1.7. Sodium could not have this kind of bond because is a metal.
Ionic bonding is a bond between a metal and a nonmetal and the difference of electronegativity is higher than 1.7. Sodium can have this kind of bond it is necessary one nonmetal.
Metallic, sodium has a metallic bond because this bond is characteristic of metals.
