Final answer:
The π electron energy in an antiaromatic ring is typically higher and less stable when compared to an open-chain structure, due to destabilization that comes from ineffective delocalization of electrons.
Step-by-step explanation:
The energy of π electrons in an antiaromatic ring compared to an open-chain structure is intertwined with the molecular orbital theory of conjugated systems. Antiaromatic compounds are less stable than their non-cyclic counterparts because the pi electron conjugation that typically stabilizes aromatic rings leads to destabilization in antiaromatic systems due to their inability to delocalize electrons across the ring effectively.
In contrast, a molecule like 1,3-butadiene shows a more stable system with a smaller HOMO-LUMO gap, leading to lower energy transitions and the ability to absorb UV light with a wavelength of 217 nm. This demonstrates stability through the conjugation of pi electrons across the double bonds. An antiaromatic ring would, however, have higher energy molecular orbitals compared to its open-chain counterpart, translating into an overall less stable and higher energy configuration.