Question

WHY DOES THE THIRD PERIOD HAVE ONLY 8 ELEMENTS ?

Answer 1

The modern periodic table is arranged in order of increasing atomic number and the elements of the similar properties are placed in the same group. In this way modern periodic table is arranged and from this arrangement we get 2 elements in first period, 8 elements in second and third period , 18 elements in 4^th, 5^th period and so on.