Difference WikiChemistry

Difference Between Atomic Orbital and Molecular Orbital

Main Difference

The main difference between Atomic Orbital and Molecular Orbital is that Atomic Orbital contains electrons that are influenced by one positive nucleus, whereas the Molecular Orbital contains electrons that are influenced by more than two nuclei depending upon the number of atoms in a molecule.

Atomic Orbital vs. Molecular Orbital

An atomic orbital is considered as the region which consists of the highest possibility of finding an electron in an atom. In contrast, the molecular orbital is considered as the region consisting of the highest possibility of finding an electron of a molecule. Electron cloud around the atom is responsible for producing the atomic orbitals, whereas the fusion of atomic orbitals that consist of relatively the same energy is responsible for producing the molecular orbitals.

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The type of atomic orbitals such as s, p, d, or f determined the shape of the atomic orbitals; on the flip side, the shape of the atomic orbitals that make up the molecule determines the shape of the molecular orbital. The Schrodinger equation is used in atomic orbitals, whereas, in molecular orbitals, the Linear combination of atomic orbitals is generally used.

The electron cloud in atomic orbitals can be affected by a single nucleus, while the electron cloud in molecular orbitals can be affected by the two or more nuclei. An atomic orbital is known to be monocentric as it is present nearby a single nucleus, while the molecular orbital is called polycentric as it is found nearby two or many different nuclei.

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Atomic orbitals are found as a, p, d, and f, while molecular orbital consists of two types as bonding molecular orbitals or antibonding molecular orbitals. The electronic configuration within the atomic orbitals does not affect the constancy of an atom, whereas the electronic configuration in molecular orbital does affect the stability of the molecule.

Comparison Chart

Atomic OrbitalMolecular Orbital
A scientific purpose that defines the wave-like behavior of either a single electron or a pair of electrons in an atom is known as atomic orbital.A scientific purpose that defines the wave-like behavior of a single electron in a molecule is known as molecular orbital.
Theory
The region which consists of the highest possibility of finding an electron in an atomThe region consisting of the highest possibility of finding an electron of a molecule
Formation
Electron cloud around the atom is responsible for the formation of atomic orbitalsThe fusion of atomic orbitals that consist of relatively the same energy is responsible for the formation of molecular orbitals
Shape
The type of atomic orbitals such as s, p, d, or f determined the shapeThe shape of the atomic orbitals that make up the molecule determines the shape
Describing the Electron Density
The Schrodinger equation is used in describing the electron densityLinear combination of atomic orbitals (LCAO) is typically used in describing the electron density
Nucleus
Monocentric as it is present nearby a single nucleusPolycentric as it is found nearby two or many different nuclei
Effect of Nucleus
The electron cloud can be affected by a single nucleusThe electron cloud can be affected by the two or more nuclei
Types and Nomenclature
Found as a, p, d, and fConsist of two types as bonding molecular orbitals or antibonding molecular orbitals
Affect of Electronic Configuration
The electronic configuration does not affect the stability of an atomThe electronic configuration does affect the stability of the molecule
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What is Atomic Orbital?

The region, which consists of the highest possibility of finding an electron is known as the atomic orbital. The possibility of the position of an atomic electron can be explained by quantum mechanics. But quantum mechanics is not able to explain the particular energy of an electron at a certain quick of time. This particular energy is explained in Heisenberg’s uncertainty principle.

The solutions of the Schrodinger equation are used to found the electron density of a given atom. A maximum of two electrons can be present in an atomic orbital. An atomic orbital is categorized by sublevels as s, p, d, and f. The orbitals of these sublevels contain different shapes.

The sublevel s orbital is found spherical and contains a maximum of two electrons and consists of only one sub-energy level. The shape of the p orbital is a dumbbell and contains up to six electrons. Three sub energy stages are present in it.

The d and f orbitals contain more composite shapes as d orbital contains five sub-energy levels and consist of up to 10 electrons. While the f orbital contains seven sub-energy levels and has a maximum of ten to fifteen electrons. The energy levels of orbitals are present in the direction of s<p<d<f.

What is Molecular Orbital?

The molecular orbital theory has explained the properties of molecular orbitals. The molecular orbital theory was first given by F. Hund and R.S. Mulliken in 1932.

According to the molecular orbital theory, when atoms joined together to give a molecule, the atomic orbitals which are overlapped usually lose their shape because of the influence of the nuclei. The novel orbitals that occur in molecules are now known as molecular orbitals.

The fusion of atomic orbitals that consist of relatively the same energy is responsible for producing the molecular orbitals. The molecular orbitals do not belong to only one atom in a molecule like in the atomic orbital, but it fits into the nuclei of all atoms which form the molecule. So, the nuclei of many different atoms act as a polycentric nucleus.

The final shape of the molecular orbitals is complicated because the shape of the atomic orbitals which construct the molecules usually determines the shape of the molecular orbitals. Accordance with Aufbau rule, the molecular orbitals are generally filled in order of low energy orbital towards a high energy orbital.

Key Differences

  1. The electron present in an atomic orbital usually is under the influence of only one positive nucleus of the atom; on the other hand, the electron present in a molecular orbital is under the influence of two or many nuclei resting on the number of atoms occur in the molecule.
  2. Atomic orbitals consist of simple shapes as s, p, d, and f determines the shape of atomic orbitals; on its contrary, the molecular orbitals consist of complex shapes because the shape of the atomic orbitals which construct the molecules usually determines the shape of the molecular orbitals.
  3. An atomic orbital is present around the single nucleus, so it is known as monocentric, while the molecular orbital is present around many different nuclei, so it is known as polycentric.
  4. In atomic orbitals, a single nucleus usually affects the electron cloud; on the contrary, in molecular orbitals, two or more than two nuclei affect the electron cloud.
  5. The electron density in atomic orbitals can be described by using the Schrodinger equation. In contrast, the electron density in molecular orbitals can generally be described by using the Linear combination of atomic orbitals (LCAO).

Conclusion

The above discussion concludes that the properties of atomic orbitals can be determined by the single nucleus of the atoms. In contrast, the molecular orbital properties can be determined by the fusion of atomic orbitals, which constructs the molecule.

Harlon Moss

Harlon currently works as a quality moderator and content writer for Difference Wiki. He graduated from the University of California in 2010 with a degree in Computer Science. Follow him on Twitter @HarlonMoss