Home › MCQs › EEJ MAIN Chemistry › Question #5552
Back to Questions
EEJ MAIN Chemistry QUESTION #5552
Question 1
According to Molecular Orbital Theory, which of the following species will NOT be a stable molecule?
  • $H_2^-$
  • $H_2^{2-}$✔️
  • $He_2^{2+}$
  • $He_2^+$
Correct Answer Explanation
Bond order for $H_2^{2-}$: 2 bonding + 2 antibonding electrons = BO = 0 → unstable. $H_2^-$: BO = 0.5 (stable). $He_2^{2+}$: 2 bonding, 0 antibonding electrons: BO = 1 (stable). $He_2^+$: BO = 0.5 (stable). Therefore $H_2^{2-}$ with BO = 0 is not a viable molecule.