Which electron configuration represents a selenium atom in an excited state? (1) 2-7-18-6 (2) 2-7-18-7 (3) 2-8-18-6 (4) 2-8-18-7

(2) 2 - 7 - 18 - 7 does, because the electron from the L shell jumped to the N shell, which requires energy.

The rest of them are either different types of atoms (different elements) or are not the excited state (ground state)