Question

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

• −13.6 eV

• −27.2 eV

• −54.4 eV

• −6.8 eV

Answer 1

−13.6 eV

Explanation:

Energy of an H-like atom in its n^th state is given by

E_n = `-"Z"^2 xx 13.6/"n"^2 "eV"`

For, first excited state of He⁺, n = 2, Z = 2

∴ `"E"_("He"^+) = -4/2^2 xx 13.6` = −13.6 eV