Question

limitations of aufbau principle​

Answer 1

Limitation of aufbau principle:

• The Aufbau principle cannot be applied to predict electron configuration of atoms on ionization.

• Although (n-1) d subshells and ns subshells lie fairly close together, yet the former is slightly higher in energy.  

• In the 6th period, 4f and 5d subshells are exceptionally close in energy.  

• When an ion is to be formed, aufbau principle doesn’t tell which electrons are to be removed.

Hope it helped............

Answer 2

The aufbau principle, from the German Aufbauprinzip (building-up principle), also called the aufbau rule, states that in the ground state of an atom or ion, electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels.