The total energy of an electron in an atom in an orbit is -3.4 eV. Its kinetic and potential energies are, respectively

Totalenergyofelectronin nth  orbit, En=-13.6Z2n2eV .  Kinetic energy of electron in nth  orbit, K.E.=13.6Z2n2eV  Potential energy of electron in nth  orbit, P.E. =-27.2Z2n2eV  Thus, total energy of electron, En=-K.E.=P.E.2 ∴  K.E. =3.4eV                                                                    Given En=-3.4eV  P.E. =2×(-3.4)=-6.8eV .