Calculate the energy required for the process  He+(g)→He2+(g)+e-. The ionization energy for the H-atom in the ground state is 2.18×10-18 J atom -1

Energy of electron in unielectron atomic system,En=-2π2mZ2e4n2h2For H-atom, ionisation energy (IE) = E∞-E1IE=0--2π2me41212h2 (where, Z=1 and n=1 for H-atom)IE=2.18×10-18 J atom -1 For He+,IE=E∞-E1=0--2π2me42212h2=4×2π2me4h2=4×2.18×10-18 J atom -1=8.72×10-18 J atom -1∴ The energy required for the process He+⟶He2++e-is 8.72×10-18 atoms -1.