Ionization energy 电离能
The ionization energy (IE) is qualitatively defined as the amount of energy required to remove the most loosely bound electron, the valence electron, of an isolated gaseous atom to form a cation. It is quantitatively expressed in symbols as:
where X is any atom or molecule capable of being ionized, X is that atom or molecule with an electron removed, and e is the removed electron. This is an endothermic process.