Final answer:
The best Lewis symbol for oxygen in O2 is :O=O:, showing a double bond and octets for each oxygen atom. This structure, however, does not explain the paramagnetic properties of oxygen, which are due to unpaired electrons not depicted in the Lewis symbol.
Step-by-step explanation:
The best Lewis symbol for oxygen, when considering the molecule O₂, is :O=O:. This Lewis structure indicates that there is an O=O double bond and each oxygen atom has eight electrons around it, satisfying the octet rule. However, this structure does not account for the paramagnetic properties of oxygen, which experimental studies have shown is due to the presence of two unpaired electrons in each oxygen molecule.
Because the Lewis structure of O₂ is expected to show all electrons as paired, there is a discrepancy with the observed magnetic behavior. Paramagnetism arises in molecules that have unpaired electrons, which is why liquid oxygen is attracted to magnetic fields despite the Lewis structure suggesting otherwise.