The first ionisation potential of Na is 5.1 eV. The value of electron gain enthalpy of Na+ will be?

The ionization energy of an atom or molecule describes the minimum amount of energy required to remove an electron from the atom or molecule in the gaseous state. But electron gain enthalpy is the amount of energy released when an isolated gaseous atom accepts an electron to become a monovalent gaseous anion. Here ∆H = -5.1 eV.