An excited-state atom is an atom in which the total energy of the electrons can be lowered by transferring one or more electrons to different orbitals. That is, in an excited-state atom not all electrons are in the lowest possible energy levels.
eg. Consider a carbon atom whose electron configuration is the following.
The total energy of the electrons in this carbon atom can be lowered by transfering an electron from a 2P orbital to the 2S orbital. Therefore, this carbon atom is an excited-state carbon atom.
see also ground-state atom
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