Why does ionization energy increase with successive electron removal, what causes the large increase from I3 to I4 in aluminum, and what is the order of increasing ionic size for aluminum ions with their reasoning?

**(i)** Ionization energy increases with each successive electron removal because the remaining electrons experience greater effective nuclear charge. **(ii)** The large increase from I3 to I4 occurs because Al³⁺ has a stable noble gas configuration (Ne-like). Removing an electron from this stable core requires significantly more energy. **(iii)** Order of increasing size: Al⁴⁺ < Al³⁺ < Al²⁺ < Al⁺ **Reason:** As electrons are removed, the remaining electrons experience stronger nuclear attraction, reducing the ionic radius.