The energy is required to remove the valance electron of a atom is called ionisation energy of atom

Ionization energyis theenergyrequired to remove an electron from a gaseousatomor ion. The first or initialionization energyor Eiof anatomor molecule is theenergyrequired to remove one mole ofelectronsfrom one mole of isolated gaseousatomsor ions.

Ionization energy is the quantity of energy that an isolated, gaseous atom in the ground electronic state must absorb to discharge an electron, resulting in a cation. This energy is usually expressed in kJ/mol, or the amount of energy it takes for all the atoms in a mole to lose one electron each.

Ionization energyis theenergyrequired to remove an electron from a gaseousatomor ion. The first or initialionization energyor Eiof anatomor molecule is theenergyrequired to remove one mole ofelectronsfrom one mole of isolated gaseousatomsor ions.

Ionization energy is the quantity of energy that an isolated, gaseous atom in the ground electronic state must absorb to discharge an electron, resulting in a cation. This energy is usually expressed in kJ/mol, or the amount of energy it takes for all the atoms in a mole to lose one electron each.

the ionisation energy is the amount of energy required to remove the most loosely bound electron which is at Valence shell

It is the minimum amount of energy required to remove electro from gaseous atom.