Question

how would you justify the presence of 18 elements in the 5th period of periodic table
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Answer 1

In 5th period the filling of 5s, 5p, 5d orbitals take place..

2of s+ 6of p+ 10of d=18

Hence 18 electrons, so 18elements are there in 5th period..

Answer 2

Explanation:

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 < 4d < 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 $\sf{5}^{th}$ period.