Question

Why Na+ has higher ionisation enthalpy than Neon though both have same numbers of electrons?

Answer 1

This is because of the following reasons :
1.Na+ have stable configuration so to gain one electron it requires large energy.
2.Na+ already have one electron less so it will have small size than parent atom so so there is an internuclear repulsion between valence electrons due to less space so it becomes difficult for Na+ to take one more electron so ionisation enthalpy increases.