Q20. A hydrogen atom has only one electron, so mutual repulsion between electrons is absent. However, in multielectron atoms mutual repulsion between the electrons is significant. How does this affect the energy of an electron in the orbitals of the same principal quantum number in multielectron atoms?
Answer. The principal quantum number determines the energy of an electron in a hydrogen atom. As a result, the energy of the orbitals increases in the following way: 1s < 2s = 2p < 3s = 3p = 3d < 4s = 4p = 4f < (2.23) Unlike the hydrogen atom, the energy of an electron in a multielectron atom is determined not only by its principal quantum number (shell) but also by its azimuthal quantum number (subshell). That is, for a given principal quantum number, the energies of s,p,d,f…. are all different.
