alleryFor a hydrogen-like ion of atomic number Z, the energy of the nth level is
AE_n = −13.6 Z² / n² eV
BE_n = −13.6 Z / n eV
CE_n = −13.6 / (Z n²) eV
DE_n = 13.6 Z² × n² eV
Answer & Solution
Correct answer: A. E_n = −13.6 Z² / n² eV
1. Bohr's formula for one-electron ions: E_n = −13.6 (Z²/n²) eV.
2. Nuclear charge Z increases attraction, deepening the energy well by Z².
3. For He⁺ (Z = 2), n = 1 gives E₁ = −13.6 × 4 = −54.4 eV.
4. The formula assumes a single electron; it fails for multi-electron atoms.
_Source: syllabus Chemistry, Ch 2 "Structure of Atom", §2.4_
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