Difference Between Atomic Orbital and Molecular Orbital

The main difference between atomic orbital and molecular orbital is that atomic orbital contains electrons that are influenced by positive nucleus while molecular orbital contains electrons that are influenced by more than two nuclei depending on the number of atoms in a molecule. …

Atomic Orbital vs. Molecular Orbital

An atomic orbital is considered to be the region that has the highest chance of finding an electron in an atom. On the contrary, the molecular orbital is considered as the region that has the highest chance of finding an electron from a molecule. The cloud of electrons around the atom is responsible for producing the atomic orbitals, while the fusion of atomic orbitals consisting of relatively the same energy is responsible for producing the molecular orbitals.

The type of atomic orbitals like s, p, dof determined the shape of the atomic orbitals; on the other hand, 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 two or more nuclei. An atomic orbital is known to be monocentric as it is present near only one nucleus while molecular orbital is called polycentric because it is found near two or many different nuclei.

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

What is Atomic Orbital?

The region, which has the highest chance 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 in a certain period of time. This particular energy is explained in Heisenberg’s uncertainty principle.

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

The d and f orbitals contain more compound forms, as the d orbital contains five subenergy levels and consists 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 the orbitals are present in the direction of s <p <d <f.

What is Molecular Orbital?

Molecular orbital theory has explained the properties of molecular orbitals. The molecular orbital theory was first put forward by F. Hund and RS Mulliken in 1932.

According to molecular orbital theory, when atoms come together to form a molecule, the overlapping atomic orbitals usually lose their shape due to the influence of the nuclei. The new orbitals found 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. Molecular orbitals do not belong to a single atom in a molecule as in the atomic orbital, but instead fit into the nuclei of all the atoms that make up the molecule. So the nuclei of many different atoms act as a polycentric nucleus.

Key differences

1. The electron present in an atomic orbital is usually under the influence of a single 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 found in the molecule.
2. Atomic orbitals consist of simple shapes, since s, p, d and f determine the shape of atomic orbitals; In contrast, molecular orbitals consist of complex shapes because the shape of the atomic orbitals that make up the molecules usually determine the shape of the molecular orbitals.
3. One atomic orbital is present around single nucleus hence it is known as monocentric while molecular orbital is present around many different nuclei thus 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 density of electrons in atomic orbitals can be described using the Schrodinger equation. In contrast, the density of electrons in molecular orbitals can generally be described using the Linear Combination of Atomic Orbitals (LCAO).

Final Thoughts

The above discussion concludes that the properties of atomic orbitals can be determined by the single nucleus of atoms. Rather, the properties of molecular orbitals can be determined by merging atomic orbitals, which build the molecule.