Carbon Energy Levels

The ground state electron configuration of carbon is 1s²2s²2p². For excited states, the most typical situation is that five of the electrons maintain the configuration 1s²2s²2p¹ and a single electron is elevated. The states in the above diagram use the spectroscopic notation to characterize the state of that one electron. However, three of the levels in the diagram have the configuration 1s²2s¹2p³ and are denoted 2p³.

The lines connecting levels indicate radiative transitions, which are subject to selection rules depending upon the angular momenta.