'Dot and cross' diagrams can show what happens to the electrons in ionic bonds.
Sodium Chloride (NaCl)
The sodium atom gives up its outer electron, becoming a sodium Na+ ion. The chlorine atom picks up the electron, becoming a Cl- (chloride) ion.
Magnesium Oxide (MgO)
The magnesium atom gives up its two outer electrons, becoming an Mg2+ ion. The oxygen atom picks up the electrons, becoming an O2- (oxide) ion.
Sodium Oxide (Na20)
The sodium atoms give up their outer electrons, becoming…