The ionization enthalpy of hydrogen atom is 1.312×106 J mol-1. The energy required to excite the electron in the atoms from n1=1 to n2=2 is

Ionisation enthalpy of hydrogen atom is 1.312×106 J mol-1. It suggests that the energy of electron in the ground state (first orbit) is -1.312×106 J mol-1.ΔE=E2-E1=-1.312×10622--1.312×1061=9.84×105 J mol-1