Question

Which best describes ionization energy?
energy needed to add an electron to a neutral atom in the gas phase
energy needed to add an electron to a neutral atom in the liquid phase
energy needed to remove an electron from an atom or ion in the gas phase
energy needed to remove an electron from an atom or ion in the liquid phase

Answer 1

Energy required to remove an electron from a neutral atom, or ion in gaseous phase.

Answer 2

Well another way to think about it is the amount of energy needed to remove your least tightly bound electron in a neutral atom in gaseous phase.

Answer 3

Your least tightly bound electrons will be in your valence shell.