i. Aufbau principle gives the sequence in which various orbitals are filled with electrons.
ii. In the ground state of an atom, the orbitals are filled with electrons based on increasing order of energies of orbitals, Pauli’s exclusion principle and Hund’s rule of maximum multiplicity.
iii. Increasing order of energies of orbitals :
- Orbitals are filled in order of increasing value of (n + l)
- In cases where the two orbitals have same value of (n + l), the orbital with lower value of n is filled first.
iv. The increasing order of energy of different orbitals in a multi-electron atom is :
1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p < 7s and so on.
