Answer:
Ionization energy is the one you need to remove an electron from an atom.
Step-by-step explanation:
when you want to form an ion, you need to take an electron from the base form (neutral form) of an atom, in that way the negative and the positive charges are not going to be equal, so is going to be an ion. In the case of the second ionization energy, you need more energy to take a second electron from this atom because is closer to the core of the atom, and it has a stronger attraction by the positive core of the ion.