For instance, Consider an electron in the second energy level (n = 2) and the p subshell (l = 1). The energy associated with this orbital represents the minimum energy required to move the electron from the p orbital to infinity or the energy released when an electron is added to the p orbital from infinity.
Energy of Orbital in Hydrogen (single-electron atom)
- In Hydrogen, the energy of orbitals is solely dependent on the principal quantum number (n).
- Consequently, the 2s and 2p orbitals in a Hydrogen atom have the same energy level.
- The 1s orbital in a Hydrogen atom is considered the most stable condition and is termed the ground state.
- Any orbital beyond 1s in a Hydrogen atom has higher energy and is referred to as an excited state.
Energy of Orbital in Multi-Electron Atom
- The energy of orbitals in multi-electron atoms depends on both the principal quantum number (n) or shells and the azimuthal quantum number (l) or subshells.
- For a given principal quantum number, such as 3, the energies of the different subshells (3s, 3p, and 3d) will be distinct.
- The variation in energies among subshells in the same shell is attributed to mutual repulsion among electrons in multi-electron atoms.
- The stability of a multi-electron atom is maintained by a greater attractive force between the nucleus and electrons compared to the repulsive forces between electrons in different shells.
- Electrons in the inner shell shield the outer shell electrons, preventing them from experiencing the full positive charge of the nucleus. This phenomenon is known as the shielding effect.
- The net nuclear charge felt by an outer shell electron, accounting for the shielding effect, is termed the effective nuclear charge.