The energy of an electron in the second orbit of a hydrogen atom is -5.45 × 10⁻¹⁹ J. What is its energy in the fourth or
E₄ = -2.18×10⁻¹⁸/16 = -1.3625×10⁻¹⁹ J.
Ref: NCERT Class 11 Chemistry > Chapter 2: Structure of Atom > Topic: Electronic Configuration - Aufbau Pauli Hund and Stability