Molecular Orbitals
Molecular Orbitals - Related Videos
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...
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...
01:27
π Molecular Orbitals of the Allyl Radical
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2025
Allyl radicals are three-carbon conjugated systems. They are readily formed as intermediates in halogenation reactions of alkenes involving the addition of halogen to the allylic carbon instead of the double bond. As seen in allyl cations and anions, each of the three sp2-hybridized carbon atoms in allyl radicals has an unhybridized p orbital. These orbitals combine to give three π molecular orbitals. The allyl systems have identical molecular orbitals but differ in the number of π electrons.
01:18
Structure of Benzene: Molecular Orbital Model
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2025
According to the molecular orbital (MO) model, benzene has a planar structure with a regular hexagon of six sp2 hybridized carbons. As shown in Figure 1, each carbon is bonded to three other atoms with C–C–C and H–C–C bond angles of 120°. The C–H bond length is 109 pm, and the C–C bond length is 139 pm which is midway between the single bond length of sp3 hybridized carbons (154 pm) and sp2 hybridized carbons (133 pm). The carbon atoms also have an unhybridized 2p atomic orbital with one...
FAQs
Energy matching and symmetry determine whether atomic orbitals can contribute effectively to a molecular orbital. Orbitals with suitable energies and compatible symmetry overlap, whereas mismatched combinations contribute less effectively or do not form the same type of interaction. This criterion helps explain why particular orbital combinations stabilize a molecule and why molecular orbital diagrams differ between molecules.
Bonding, antibonding, and nonbonding orbitals contribute differently to molecular behavior. Their relative occupancy is used to interpret bond order and molecular stability, while nonbonding electrons help distinguish electrons that do not directly alter the bonding pattern. Examining these categories therefore gives a more detailed picture than simply counting connections between atoms.
Electron placement is not arbitrary: orbitals fill according to energy, with the Pauli exclusion principle limiting the electrons in an orbital and Hund’s rule governing occupation of orbitals of comparable energy. Applying these rules to an orbital diagram helps connect the electronic arrangement with properties such as magnetism and with the energy-based description of a molecule.
To analyze a molecule, chemists can construct an orbital diagram by considering atomic orbitals with suitable energy and symmetry, identifying the resulting bonding, antibonding, or nonbonding levels, and placing electrons according to the governing rules. The completed diagram can then be used to assess bond order, stability, and other molecular properties.
When a simple bonding model does not adequately represent a molecule, molecular orbital theory is especially useful for examining electron delocalization, magnetism, and electronic spectra. Its orbitals describe electrons across the molecule rather than restricting the explanation to a localized bond picture. That broader view can reveal structural or electronic behavior that simpler models may not fully capture.
Computational models extend orbital analysis beyond a hand-drawn diagram. Using the same principles of orbital formation and electron occupation, they help predict molecular structure, reactivity, and properties. In chemistry research, these predictions provide a way to connect an electronic description with observable behavior, while orbital diagrams offer a more direct conceptual representation of the same analysis.