• # question_answer 14) On the basis of quantum numbers, justify that sixth period of the periodic table should have 32 elements.

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.