Question

Generally first, second and third period consists of 2, 8, 8 elements. Why this is so ?​

Answer 1

Answer:

In the first period, it is completed. Its capacity is of two electrons.

In the second period 2s and 2p and in the third period 3s and 3p are completed. The capacity of these subshells is of 8 electrons each.

Thus, 2, 8 and 8 elements are present in the first, second and third periods respectively.