How would you justify the presence of 18 elements in the 5^(th) period of the periodic table?

How would you justify the presence of 18 elements in the 5^(th) period

1.	How would you justify the presence of 18 elements in the 5^(th) period of the periodic table?
Answer» Solution :When n = 5, 1 = 0, 1, 2 , 2, 3. The order in which the energy of the available orbitals 4d, 5s and 5p increases in `5s lt 4d lt 5p`. The total number of orbitals available are 9. The maximum number of ELECTRONS that can be accommodated is 18 and THEREFORE 18 ELEMENTS are there in the `5^(th)` PERIOD.