Period  3 elements i.e. Na, Mg, Al, Si, P, S, Cl, Ar are also called typical elements,that can summarise the properties of their respective groups. Period 3 elements along with period 2 elements are called short periods. Period 3 elements contains elements of Gr. IA, IIA, IIIA, IVA, VA, VIA, VIIA & Zero, hence these elements also belong to representatives elements or normal elements.In this period Na is largest in size Cl is smallest , Ar is an exception because it is an inert gas. The elements of this period Mg & P shows an exception in their ionisation potential.The elements of this period also shows the property of diagonal relationship with the elements of the second period.