question_answer 14)

On the basis of quantum numbers, justify that sixth period of the periodic table should have 32 elements.

Answer:

The sixth period corresponds to the filling of principal energy level 6, i.e., \[n=6\] or \[6s,\text{ }6p,\]\[6d\] and \[6f-\]orbitals. The \[6d\] and \[6f-\]orbitals have higher energy than 7\[7s-\]orbital. Thus, \[6d\] and \[6f-\]orbitals are not filled. However, before \[6p-\]orbitals \[4f\] and \[5d\]-orbitals which have energies between 6s and \[6p-\]orbitals are being filled. Thus, sixteen orbitals, i.e., \[6s,4f,5d\] and \[6p\]-orbitals receive electrons corresponding to 32 elements. Therefore, sixth period accommodates 32 elements.