How does a molecular orbital differ from an atomic orbital? | Socratic
In chemistry, molecular orbital (MO) theory is a method for describing the electronic structure of molecules. Electrons are not assigned to individual bonds between atoms, but are. Describe the relationship between atomic and molecular orbitals Describe how VSEPR theory helps predict the shape of molecules Identify ways in which orbital . atomic orbital: 1. electron in an AO is under the influence of only one nucleus What is the difference between atomic and molecular orbitals with reference to energy? .. The answer is that there is a deep connection between gravitation and.
Overview[ edit ] MO theory provides a global, delocalized perspective on chemical bonding. In MO theory, any electron in a molecule may be found anywhere in the molecule, since quantum conditions allow electrons to travel under the influence of an arbitrarily large number of nuclei, as long as they are in eigenstates permitted by certain quantum rules.
Thus, when excited with the requisite amount of energy through high-frequency light or other means, electrons can transition to higher-energy molecular orbitals. For instance, in the simple case of a hydrogen diatomic molecule, promotion of a single electron from a bonding orbital to an antibonding orbital can occur under UV radiation.
This promotion weakens the bond between the two hydrogen atoms and can lead to photodissociation—the breaking of a chemical bond due to the absorption of light. Although in MO theory some molecular orbitals may hold electrons that are more localized between specific pairs of molecular atoms, other orbitals may hold electrons that are spread more uniformly over the molecule.
Thus, overall, bonding is far more delocalized in MO theory, which makes it more applicable to resonant molecules that have equivalent non-integer bond orders than valence bond VB theory.
This makes MO theory more useful for the description of extended systems.
Molecular orbital theory - Wikipedia
An example is the MO description of benzeneC 6H 6, which is an aromatic hexagonal ring of six carbon atoms and three double bonds. Two of these electrons are in an MO that has equal orbital contributions from all six atoms.
The other four electrons are in orbitals with vertical nodes at right angles to each other. All carbon-carbon bonds in benzene are chemically equivalent. Structure of benzene In molecules such as methaneCH 4, the eight valence electrons are found in four MOs that are spread out over all five atoms.
How does a molecular orbital differ from an atomic orbital?
However, it is possible to transform the MOs into four localized sp3 orbitals. Linus Pauling, inhybridized the carbon 2s and 2p orbitals so that they pointed directly at the hydrogen 1s basis functions and featured maximal overlap.
- Difference Between Atomic Orbital and Molecular Orbital
However, the delocalized MO description is more appropriate for predicting ionization energies and the positions of spectral absorption bands. When methane is ionized, a single electron is taken from the valence MOs, which can come from the s bonding or the triply degenerate p bonding levels, yielding two ionization energies.
In comparison, the explanation in VB theory is more complicated. When one electron is removed from an sp3 orbital, resonance is invoked between four valence bond structures, each of which has a single one-electron bond and three two-electron bonds.
The difference in energy between the ionized and ground state gives the two ionization energies. This results from continuous band overlap of half-filled p orbitals and explains electrical conduction. Molecular orbitals are formed by the combination of nearly the same energy atomic orbitals. Unlike atomic orbitals, the molecular orbitals do not belong to a single atom in a molecule but belong to nuclei of all the atoms which make the molecule. Thus, the nuclei of different atoms behave as a polycentric nucleus.
The final shape of the molecular orbital depends on the shapes of atomic orbitals that make the molecule.
Molecular orbital theory
According to Aufbau rule, the molecular orbitals are filled from low energy orbital to high energy orbital. Like an atomic orbital, a molecular orbital can hold a maximum number of two electrons. The behavior of the electron in a molecular orbital can be described by using the Schrodinger equation.
However, due to the complexity of molecules, the application of Schrodinger equation is quite difficult. Hence, scientists have developed a method for approximate evaluation of the behavior of electrons in a molecule.
The method is called linear combination of atomic orbitals LCAO method. Atomic orbital is the region having the highest probability of finding an electron in an atom. Molecular orbital is the region having the highest probability of finding an electron of a molecule. Atomic orbitals are formed by the electron cloud around the atom.
Molecular orbitals are formed by the fusion of atomic orbitals that have nearly the same energy. The shape of atomic orbitals is determined by the type of the atomic orbital s,p,d or f.
The shape of the molecular orbital is determined the shapes of atomic orbitals that make the molecule.Molecular Orbital Theory vs Valence Bond
Describing the Electron Density Atomic Orbital: Schrodinger equation is used. Linear combination of atomic orbitals LCAO is used. Atomic orbital is monocentric as it is found around a single nucleus.
Molecular orbital is polycentric as it is found around different nuclei. Effect of Nucleus Atomic Orbital: Single nucleus affects the electron cloud in atomic orbitals Molecular Orbital: Two more nuclei affect the electron cloud in molecular orbitals.