Which of the following atoms/ions have a ground state energy of -54.4 eV?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Singly-ionised helium
Total energy of a hydrogen-like ion, having z protons in its nucleus -
$E=\frac{-B.6z^2}{n^2}eV$ [n = Principle quantum number]
for He atom, z = 2
$E=\frac{-13.6×4}{n^2}eV=\frac{-54.4}{n^2}eV$
$∴E=\frac{-54.4}{(1)^2}eV=-54.4$