A Evolução da Teoria dos Orbitais Moleculares: De Fundamento Revolucionário à Revisão Conceitual

Resumo

The Molecular Orbital Theory (MO theory), introduced by Robert S. Mulliken in 1928, laid the foundation
for modern quantum chemistry by proposing that electrons in molecules occupy orbitals delocalized across
the entire structure. This article revisits the conceptual basis of the traditional Linear Combination of Atomic
Orbitals (LCAO-MO) approach, highlighting its historical relevance alongside intrinsic limitations, such
as basis set dependence, imposed orthogonality, and the non-observable nature of canonical orbitals. While
LCAO-based orbitals remain powerful interpretative tools, their physical interpretation requires caution
and critical examination. The article concludes by reinforcing the importance of ongoing conceptual
refinement, even in long-established quantum chemical frameworks.
Keywords: Molecular orbital theory; basis sets; delocalized orbitals; floating basis functions.