Valence electrons are the electrons present in the outermost shell of an atom and have the highest energy level of an atom whereas electrons at ground state or lower orbitals have less potential energy.
This is so because <u>orbitals nearby nucleus are strongly bonded with the atomic nucleus and have less energy than an outermost shell.</u>
So, the potential energy states of an atom depend on the number of orbitals. In the given options fluorine with atomic number 9 has less number of orbitals that is 2 orbitals and valence electrons will be present in second orbitals, so fluorine will have the lowest average potential energy states.
) ions in aqueous solution.