Question

How would you justify the presence of 18 elements in the 5th period of the Period Table?​

Answer 1

Answer:

When n=5,l=0,1,2,3 and 4. The order in which the enery of the available orbitals 4d,5s and 5p increases in 5s<4d<5p. The total number of orbitals available is 9. The maximum number of electrons that can be accommodated is 18, and therefore 18 elements are there in the 5th period.