1. The energy required to remove the first electron outermost orbit of a neutral gaseous atom of the element is called first ionization energy.
2. The energy required to remove from unipositive ion of the element is called second ionization energy.
3. Second ionization energy is always more than first ionization energy because it is difficult to move electron from unipositive ion due to greater nuclear attraction.
4. So it is difficult to remove an electron from Mg+ when compared with Mg.
