Electronic configuration of multielectron atoms can be written by the use of four quantum numbers and also by following certain principles. Pauli's exclusion principle suggests that maximum capacity of an atomic orbital is two. Auf bau principle suggests that the lower energy orbitals are filled first and hence stability can be attained. Hunds rule of maximum multiplicity suggests that pairing occurs with one electron. The arrangement of electrons in the space around the nucleus can be understood only after writing the electronic configuration. Thus writing electronic configuration is more important in the structure of an atom.
Auf-bau principle is first violated for the element with atomic numbers

Options

A. 21
B. 24
C. 26
D. 29

Answer

B