The correct option is D −82 kJ mol−1
From Bohr's theory, if an electron of an hydrogen atom, orbits in orbit ′n′ with energy ′E′n, then, En∝1n2
Since, Z = 1 for H-atom
So,
Ratio of energies for 2nd orbit (n2=2) and 4th orbit (n4=4) is,
E2E4=n24n22=41
∴E4=E24=−82 KJ mol−1