Question

While filling up of electrons in the atomic orbitals,the 4s orbital is filled before the 3d orbital but reverse happens during the ionization of the atom.Explain why?

Answer 1

While filling up of electrons in the atomic orbitals,the 4s orbital is filled before the 3d orbital but reverse happens during the ionization of the atom.

Explanation:

Atomic orbitals are filled in order of increasing energies. Since the energy of 3d orbital is more than 4s orbital, on the basis of (n+l) rule, it is filled after 4s orbital. But during ionization, electrons in the outermost orbital are lost. Since, 4s will be the outermost orbital in this case; electrons from this orbital will be ionized first.