The ionization energies for removing successive electrons from sodium are 496 kJ/mol, 4562 kJ/mol, 6912 kJ/mol, and 9544 kJ/mol. The great jump in ionization energy after the first electron is removed indicates that

The great jump in ionization energy indicates that the most stable form of the sodium atom- the noble gas configuration, was reached after the removal of the first electron.

Explanation:

Sodium atom has an electronic configuration of 2,8,1. After the first electron has been removed from a sodium atom, the ion formed now has a noble gas configuration which assigns stability to it.

Noble gases have very high ionization energy due to the stability conferred on the by virtue of their completely filled outermost shells. They do not have need to lose electrons to attain stability. Also, because they have the most protons of their period, their atomic radius is reduced as electrons are pulled into the nucleus.

So, the great jump in ionization energy indicates that the most stable form of the sodium atom- the noble gas configuration, was reached after the removal of the first electron.