The energy of electron in first Bohr's orbit of H-atom is -13.6 eV. What will be its potential energy in n = 4th orbit.

Energy of nth orbit of H-atom                         =−2π2me4k2h2×  1n2Energy of  first Bohr's orbit of H-atom                                       =−2π2me4k2h2                                             =-13.6 eV (given)Energy of fourth Bohr's orbit of H-atom=−2π2me4k2h2×  142=13.6  ×  116eV=−0.85  eV   (or)  En=E1n2×Z2=-13.622(12)=-0.85eV       PE of electron in nth orbit = 2 ×  EnSo P.E. of electron in 4th orbit = 2 ×  −0.85  =  −1.70  eV