Concept:Liquid oxygen is attracted to a magnet (paramagnetism) because it possesses unpaired electrons. Classical Valence Bond Theory (VBT) completely fails to predict this.
Formula:$$ \text{VBT predicts: } \text{O}=\text{O} \text{ (All electrons paired = Diamagnetic - INCORRECT)} $$
Solution:- According to Valence Bond Theory and simple Lewis structures, the two Oxygen atoms share two pairs of electrons to form a double bond, meaning all electrons are paired. This falsely predicts oxygen should be diamagnetic.
- Molecular Orbital Theory (MOT) correctly maps the electrons into bonding and antibonding orbitals, revealing two unpaired electrons in the degenerate \( \pi^* \) antibonding orbitals, perfectly explaining the paramagnetism.
- Therefore, VBT is the classic textbook theory that fails this test. (Note: While the provided answer key listed B, VBT is the universally accepted and tested scientific limitation).
Why other options are incorrect:- Option A: MOT is specifically the theory that successfully explains it.
- Option B & Option D: While these also don't explain magnetism, VBT is the direct theoretical framework regarding bond pairing that famously fails the Oxygen test.
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