How many elements are present in the `5 ^(th) ` period of the long form peripodic table ? Give a possible reason .

Explanation

The `5^(th) ` period starts with the filling of 5x level . It ends when the 5P level is complete The sub energy levels filled in the sequence are 5s, 4d , 5p . Then total number of electrons filled into these levels is 18. Hence the total number of elements in the period is 18. THe `15 ^(th) ` period starts with Rubidium (Rb ) and ends with Xenon (Xe ) .