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

Explanation:

Ionization energy is defined as the energy required to remove an electron from an atom or ion in the gas - phase. Adding an electron is related to electron - affinity, and the phase considered for ionization energy is gas - phase, not liquid - phase.

Answer:

energy needed to remove an electron from an atom or ion in the gas phase