How does the successive ionization energies of an element relate to its reactivity?

Successive ionization energies measure how hard it is to remove each electron from an atom. The first few ionization energies are low for elements that easily lose or gain electrons, so they react readily. When the next ionization energy jumps sharply, the atom has reached a stable electron configuration, making it harder to remove another electron and reducing its reactivity. For example, sodium has a very low first ionization energy and reacts quickly, but its second ionization energy is so high that it rarely loses a second electron, so its chemistry is dominated by the loss of one electron. Thus, elements with low successive ionization energies tend to be more reactive because their electrons are easier to remove or share.