1st Ionization energy of Na is lower than Mg but it is reverse in case of 2nd ionization energy . explain

The first ionisation energy of sodium is less than Magnesium because Magnesium is smaller is size than sodium. This is because the nuclear charge in  Magnesium is more than sodium. Thus there are increased electrostatic attraction in Magnesium atom which draws the orbital electrons closer to the nucleus. As a result, the electrons are held more tightly in magnesium, because of which the energy is needed to remove the first electron (first ionisation energy) is greater than sodium. However, after losing the outermost electron, the sodium atom attains a noble gas configuration, which is very stable. Hence in sodium ion the second ionisation energy corresponds to removing the second electron from a closed shell. On the other hand Mg⁺ ion still has one more electron in the valence shell. Hence the Mg⁺ ion can lose the second electron much easily to for Mg⁺² ion than Na⁺ ion.