Q. Consider the following statements:
  1. Oxygen has the highest electronegativity of all known elements.
  2. It exists as O₂ under normal conditions and as O₃ in the stratosphere.
  3. Oxygen is paramagnetic due to the presence of unpaired electrons in its molecular orbital.
Which of the above statements is / are correct?

Answer: Only 2 and 3
Notes: Oxygen does not have the highest electronegativity; fluorine is more electronegative. Oxygen exists as O₂ in normal conditions and as O₃ (ozone) in the stratosphere. Molecular O₂ is paramagnetic due to two unpaired electrons in its antibonding molecular orbitals. Thus, only statements 2 and 3 are correct.