Molekyyliorbitaaliyhteyksillä

Molekyyliorbitaaliyhteyksillä, often referred to as Molecular Orbital Theory (MO theory) in English, is a theoretical model used in chemistry to describe chemical bonding. It proposes that when atoms combine to form a molecule, their atomic orbitals merge to form new molecular orbitals that span the entire molecule. These molecular orbitals are then filled with electrons according to the Aufbau principle, Hund's rule, and the Pauli exclusion principle.

Molecular orbitals can be classified as either bonding or antibonding. Bonding molecular orbitals are lower in energy than the original atomic orbitals and are stabilized by the constructive interference of atomic orbital wave functions. Electrons occupying bonding orbitals contribute to the formation of a stable chemical bond. Antibonding molecular orbitals, conversely, are higher in energy and arise from the destructive interference of atomic orbital wave functions. Electrons in antibonding orbitals weaken the bond. The difference in energy between bonding and antibonding orbitals is known as the energy gap.

The number of electrons in bonding and antibonding orbitals determines the stability and bond order of a molecule. A positive bond order indicates a stable molecule, while a zero or negative bond order suggests that the molecule is unstable and will not form. MO theory is a powerful tool for explaining phenomena such as magnetism, bond lengths, and the electronic spectra of molecules, offering a more comprehensive understanding of chemical bonding than simpler models like Valence Bond Theory.