The energy of a hydrogen atom in the ground state is -13.6 eV. The energy of a He⁺ ion in the first excited state will be

Options

(a) – 13.6 eV
(b) – 27.7 eV
(c) – 54.4 eV
(d) – 6.8 eV

Correct Answer:

– 13.6 eV

Explanation:

energy of a H-like atom in its nth state is given by
E = – Z² x 13.6 / n² eV
For, first excited state of He⁺, n= 2, Z= 2
Eₕₑ⁺ = – 4/2² x 13.6 = – 13.6 eV