Molecular Orbital Theory
Molecular Orbital Theory - Related Videos
10:18
Molecular Orbital (MO) Theory
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2023
Source: Tamara M. Powers, Department of Chemistry, Texas A&M University This protocol serves as a guide in the synthesis of two metal complexes featuring the ligand 1,1'-bis(diphenylphosphino)ferrocene (dppf): M(dppf)Cl2, where M = Ni or Pd. While both of these transition metal complexes are 4-coordinate, they exhibit different geometries at the metal center. Using molecular orbital (MO) theory in conjunction with 1H NMR and Evans method, we will determine the geometry of these two...
03:51
Molecular Orbital Theory II
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2020
Molecular Orbital Energy Diagrams The relative energy levels of atomic and molecular orbitals are typically shown in a molecular orbital diagram. For a diatomic molecule, the atomic orbitals of one atom are shown on the left, and those of the other atom are shown on the right. Each horizontal line represents one orbital that can hold two electrons. The molecular orbitals formed by the combination of the atomic orbitals are shown in the center. Dashed lines show which of the atomic orbitals...
02:35
Molecular Orbital Theory I
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2020
Overview of Molecular Orbital Theory Molecular orbital theory describes the distribution of electrons in molecules in the same way as the distribution of electrons in atoms is described using atomic orbitals. Quantum mechanics describes the behavior of an electron in a molecule by a wave function, Ψ, analogous to the behavior in an atom. Just like electrons around isolated atoms, electrons around atoms in molecules are limited to discrete (quantized) energies. The region of space in which a...
03:07
Kinetic Molecular Theory: Molecular Velocities, Temperature, and Kinetic Energy
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2020
The kinetic molecular theory qualitatively explains the behaviors described by the various gas laws. The postulates of this theory may be applied in a more quantitative fashion to derive these individual laws. Collectively, the molecules in a sample of gas have average kinetic energy and average speed; but individually, they move at different speeds. Molecules frequently undergo elastic collisions in which the momentum is conserved. Since the colliding molecules are deflected off at different...
02:35
Band Theory
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2020
When two or more atoms come together to form a molecule, their atomic orbitals combine and molecular orbitals of distinct energies result. In a solid, there are a large number of atoms, and therefore a large number of atomic orbitals that may be combined into molecular orbitals. These groups of molecular orbitals are so closely placed together to form continuous regions of energies, known as the bands. The energy difference between these bands is known as the band gap. Conductor, Semiconductor,...
FAQs
When atomic orbitals combine as linear combinations, the resulting molecular orbitals can differ in energy from the orbitals that formed them. Lower-energy combinations are bonding orbitals, while higher-energy combinations are antibonding orbitals. This energy separation provides the basis for arranging electrons and evaluating how their distribution affects a molecule’s bonding and electronic structure.
Bond order depends on the balance between electrons in bonding and antibonding molecular orbitals. A greater bonding contribution generally indicates a more stable bond, whereas antibonding occupancy reduces that contribution. Comparing these populations therefore helps chemists predict related structural properties, including bond order, bond length, and overall molecular stability.
The theory connects magnetic behavior to how electrons occupy molecular orbitals rather than treating bonding alone. For oxygen, its molecular-orbital electron population produces the magnetic behavior described as paramagnetism. This makes the model especially useful because it explains an experimentally observed property that depends on electronic structure, not simply on a molecule’s displayed bonding arrangement.
Molecular orbital theory allows electrons to be represented in orbitals extending across the molecule, so their distribution need not be assigned to individual bonds. In benzene, this framework supports interpretation of electron delocalization as a molecular property. The result is a more complete description of its electronic structure than a strictly localized picture would provide.
A typical analysis identifies the relevant atomic orbitals, combines them to form molecular orbitals, and organizes the resulting orbitals by energy. Electrons are then placed into those orbitals according to their energies and the Pauli exclusion principle. Comparing the occupied bonding and antibonding orbitals provides predictions about bond order, stability, bond length, and magnetic behavior.
A molecular orbital diagram can connect electron occupancy with several measurable or chemically useful properties. The relative populations of bonding and antibonding orbitals help predict bond order, stability, and bond length, while the overall electronic arrangement helps indicate magnetic behavior. These outcomes make the diagram useful for interpreting how electronic structure influences molecular behavior.
Because the model describes the electronic structure of an entire molecule, it provides a framework for interpreting molecular spectra and reaction behavior. Changes involving molecular orbitals can be related to electronic transitions or altered electron distributions. This broader perspective also helps connect observed chemical behavior with delocalization and the energies of bonding and antibonding orbitals.