A sodium atom and ion differ by one electron. For 100 moles each of sodium atoms and ions there would be a difference of 100 moles of electrons.
Mass of 100 moles of electrons = 5.48002 g
Mass of 1 mole of electron = 5.48002 / 100 g
Mass of one electron = (5.48002 / 100 ร 6.022 ร 1023)
= 9.1 ร 10-28 g
= 9.1 ร 10-31 kg