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

1.	How would you justify the presence of 18 elements in the 5th period of the periodic table.
Answer» Solution :When n = 5, l = 0, 1, 2, 3. The order in which the energy of the available orbitals 4d, 5s and 5P increases is 5s `gt` 4d `gt` 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 5th PERIOD.

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