1.32 explain, using dot and cross diagrams, the formation of ionic compounds by electron transfer, limited to combinations of elements from Groups 1, 2, 3 and 5, 6, 7

Dot and cross diagrams

Dot and cross diagrams are used to show electron transfers, and the creation of ions.

As you can see, the magnesium atom gives 2 electrons to the oxygen atom, so an ionic bond is created and therefore, 2 ions are created; the magnesium atom becomes a positive ion, losing 2 electrons and the oxygen atom becomes a negative ion, gaining 2 electrons.