This type of combination results in an area of zero electron density between the two nuclei, known as a nodal plane (or node). The σ* 1 s orbital is generated by a destructive combination (or interference), where the wave functions of the two atomic orbitals cancel each other. These electrons are stabilized by attractions to both nuclei, and they hold the atoms together with a covalent bond. Notice in Figure 9.19 “ Hydrogen molecular orbital combination diagram” that the electron density of this orbital is concentrated between the two nuclei. This is the lower energy of the two molecular orbitals and is known as the bonding molecular orbital. The σ 1 s orbital is generated by a constructive combination (or interference), where the two atomic orbitals wave functions reinforce (add to) each other. The Molecular Orbitals of the Hydrogen MoleculeĬombining the 1 s orbitals of each hydrogen atom using LCAO, two molecular orbitals are generated σ 1 s (pronounced sigma one s) and σ* 1 s (pronounced sigma star one s). Molecular orbitals are associated with the entire molecule, meaning the electron density is delocalized (spread out) over more than one atom. The major difference between atomic and molecular orbitals is that atomic orbitals represent electron density in space associated with a particular atom. – They can hold a maximum of two electrons of opposite spin per orbital (Pauli exclusion principle). – They are filled from lowest energy to highest energy (Aufbau principle). Molecular orbitals share many similarities with atomic orbitals:

MO theory takes the idea of atomic orbitals overlapping to a new level, where new molecular orbitals are generated using a mathematical process called linear combination of atomic orbitals (LCAO). Molecular orbital theory is a more sophisticated model for understanding the nature of chemical bonding. To complement this theory, we use another called the molecular orbital (MO) theory. Valence bond theory is able to explain many aspects of bonding, but not all. Learn to draw molecular orbital electron configuration energy diagrams.Gain an understanding of molecular orbital theory.

Orbital diagrams