The minimum amount of energy is required to remove the most loosely bound electron is known as ionization enthalpy.
The minimum amount of energy required to remove the most loosely bound selection is known as ionization enthalpy .

The ionization energy (Ei) 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 X + energy → X+ + e−
A quantitative measure of the tendency of an element to lose electron is given by its Ionization enthalpy