The ionisation energy of hydrogen atom is 13.6 eV and the first ionisation energy of helium is 24.6 eVWhat is the first ionisation energy of He+ (isoelectronic of H-atom)?What is the enthalpy change of the following process He2+(g)+2e−⟶He(g)To which of the following species the above formulae or concept is inapplicable

IHgg→  H+g+e−                         IEH=13.6 eVIIHgg→  He+g+e−                       IEHefirst=24.6 eVIIIHe+g→  He2+g+e−                 IEHesecond=?=qBy Bohr's theory of H-atomIEz=IEH=Z2n2IEHe+=13.62212= 54.4 eV  Heg→  He2+g+2e−ΔH=24.6+q=79.0 eVHence for He2+g+2e−→  HegΔH=−79.0 eVNote : Second ionisation energy He(g) is the first ionisation of He+ (g).Heg→  He+g+e−IE1  of   HegHe+g→  He2+g+e−IE2  of  HegIE1  of  He+  gBoron has five electrons and +3 means it has now two electron, the concept is mainly applicable to one electron species.