Question

How many elements are there in period 4 of the periodic table?

Answer 1

The period in the periodic table:

1. The elements in the horizontal rows of a periodic table represent periods.
2. The 4th-period elements are the elements in the 4th row of the periodic table.
   The number of elements in a period can be determined as:
   Let 'p' be the period number, and
   If p is even , the number of elements is: $(P + 2)^2/2$
   If p is odd , the number of elements is:$(P + 1)^2/2$
   Since period number is 4, it is even.
   Therefore, number of elements in period 4 will be
   $(4+2)^2/2 = 36/2 = 18$
   Hence, there are 18 elements in period 4 of the periodic table.