Discussion:
Na atom and configuration
Consider the Na atom. Although the ground state of Na atom has one and only one corresponding electron configuration, other electron configurations are certainly possible for Na atom; they correspond to higher-lying excited electronic states. The table below gives some of the possible electron configurations, term symbols, and energies (in cm^-1) of various states of Na atom. Include J in all term symbols asked for below.
(Ne) 3s 2S1/2 0.000
(Ne) 3p 2P1/2 16956.183
2P3/2 16973.379
(Ne) 4s 2S1/2 25739.86
(Ne) 3d 2D5/2 29172.855
2D3/2 29172.904
(a) What term symbol(s) arise from the [Ne]3p configuration?
(b) What term symbols arise from the [Ne]3d configuration?
(c) Using the atomic spectroscopy selection rules, list all possible transitions from state(s) arising from the [Ne] 3p configuration upwards to the state(s) arising from the [Ne] 3d configuration. Using the table, give the energy (in cm-1) and wavelength of absorbed light (in nm) for each transition.
From this example you can see that tables such as the one above allow one to predict/explain atomic spectra.