Single electron atoms
The relative energies of various orbitals of single electrons depend on the value of the principal quantum number 'n' and is independent of the value of 'l'. This can be shown by an arrangement known as energy level diagram. The diagram given below illustrates the relative energy of various energy levels for hydrogen and hydrogen like atoms.
Fig: 3.18 - Relative energy levels of hydrogen and hydrogen like atoms
Multi-electron atoms
In these atoms the energy of orbitals have the same values of 'n' but different values of 'l'. Thus both values of 'n' and 'l' determine the energy of an orbital. The following hold good for multi-electron atoms.
- Different orbitals having the same principle quantum number 'n' (sub shell) may have different energies.
- For a particular main energy level, the orbital having higher value of the azimuthal quantum number 'l' has higher energy. In general, energies of orbitals belonging to the same main energy level follow the order, 's' < 'p'< 'd'< 'f' .
- When 'n'
3 some orbitals belonging to a lower main energy level may have higher energy than some orbitals belonging to the higher main energy levels. For examples the energy of '3d' orbitals >'4s' orbitals.
- The orbital having lower (n + l) value has lower energy. However for orbitals, whose (n + l) values are equal, the orbital having lower value of n has lower energy. For example
3d orbital, n + 1 = 3 + 2 = 5.
