A sodium atom in an excited state has an electron configuration of 1s²2s²2p⁶3p¹. The excited electron within the configuration was excited from the:

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11ecba2d_124a_5a07_a3bf_11221b7aebd4_MD0008_00 Electrons around an atom can exist only in particular, discrete energy levels, which are identified by quantum numbers and by orbital designations. Electron configurations account for the locations of all electrons within the energy levels (orbital shells and subshells) of an atom or ion. Shells are indicated using the principal quantum number n, which relates to the distance of an orbital from the nucleus. Subshells are labeled by type (s, p, d, f), which relates to the shapes of the orbitals that hold a maximum of 2, 6, 10, and 14 electrons, respectively. Electron configurations are listed sequentially in order of increasing energy. In the ground state (unexcited state), the electrons of an atom occupy the lowest energy configuration. However, an electron in the ground state can temporarily achieve an excited state and jump from a lower energy orbital to a vacant higher energy orbital by absorbing energy equal to the energy difference between two levels. Upon relaxation back to the ground state, an excited electron releases the absorbed energy as a photon. According to the filling order, the lowest energy configuration (ground state) of a sodium atom is 1s²2s²2p⁶3s¹. As such, an electron configuration of 1s²2s²2p⁶3p¹ for a sodium atom in an excited state indicates that the excited atom has a vacant 3s orbital (absent in the configuration) and an excited electron in the 3p orbital. Therefore, the excited electron occupying the 3p orbital was excited from the 3s orbital. (Choices A and B) The 2s and 2p orbitals are fully occupied. Therefore, no electrons were excited from these orbitals in the ground state. (Choice D) The 3p orbital is unoccupied in the ground state and cannot be the orbital from which the electron is excited. Educational objective: Electrons typically occupy the lowest energy configuration (ground state), but an electron may achieve an excited state and temporarily jump to a higher energy orbital by absorbing energy equal to the energy difference between the two levels.

A Sodium Atom in an Excited State Has an Electron