Identify among the following which has Lowest energy of electron in 1st shell.
Correct answer: D. Be+³
- A. H
- B. He+¹
- C. Li+²
- D. Be+³
Explanation
For a hydrogen-like species in the first shell, electron energy is E = -13.6 Z^2/1^2 eV, so it becomes more negative as nuclear charge Z increases. Be3+ has Z = 4 and therefore the lowest energy, E = -13.6 x 4^2 = -217.6 eV, compared with -13.6 eV for H. The likely mistake is choosing H because it is the simplest atom, while ignoring the stronger attraction of the higher nuclear charge in these one-electron ions.
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