The Ionisation potential of Hydrogen is 2.17 × 10–11 erg/atom. The energy of the electron in the second orbit of the hydrogen atom is

Ionization potential of H-atom has the same magnitude as energy of electron in first orbit of H-atom but opposite signSo IP1 of H-atom = +2.17 × 10-11 erg/atomE1 of H-atom = -2.17 × 10-11 erg/atomE2=-Z2n2E1=-1222E1(∵Z=1)=-2.17×101122 erg/atom