There are three primary orbitals, namely, Atomic orbitals, Molecular and Hybrid Orbitals. Firstly, an orbital is a mathematically defined area encircling a nucleus of an atom or molecule that can have one, two or zero electrons. The cloudlike structures surrounding the nucleus where electrons assemble themselves are termed orbitals.

Moreover, several theories were proposed, postulating many other aspects of orbitals and related concepts. Today’s discussion will revolve around the difference between Molecular and Hybrid Orbitals. Let’s Directly Dive into the topic. 

Difference between Molecular and Hybrid orbitals: Overview

• Molecular orbitals– These orbitals are the hypothetical orbitals developed from the covalent bonding of two different atoms. During bonding, the atomic orbitals of different atoms overlap, resulting in the rise of new orbitals. 
• Hybrid orbitals– When discussing the Hybrid orbitals, these are the orbitals formed by the hybridisation process. Two or more orbitals merge and develop the same number of new orbitals of equivalent energies.  

The critical difference between Molecular and Hybrid orbitals is, Molecular orbitals are formed when orbitals of two different atoms merge. On the other hand, hybrid orbitals are formed after the connection of orbitals of the same atom. 

Origin

Molecular Orbitals

Molecular orbitals were postulated in the Molecular Orbital theory, which the scientists Mulliken and Friedrich Hund proposed in 1927. Though the molecular orbital theory is also termed as Hund-Mulliken theory. However, the theory was validated in the year 1933. 

Hybrid Orbitals

Likewise, molecular orbitals originated from the MO theory, and Hybrid orbitals were introduced in the hybridisation theory. This theory developed on the concepts of valence bond theory, and it was proposed by the American chemist Linus Pauling in 1931.  

The difference among subtypes of molecular and hybrid orbitals

Molecular and Hybrid orbitals are two broad classes of orbitals. They both have subtypes of orbitals. There are two subtypes of orbitals in molecular orbitals: bonding molecular orbitals and Antibonding molecular orbitals. On the other hand, there are five primary hybrid orbitals: sp, sp2, sp3, sp3d and sp3d2. Let’s discuss 

Molecular orbitals

• Bonding Molecular orbitals: These orbitals are usually in a stable state. This is because they generate low energy compared to the atomic orbitals. Moreover, the shape of such orbitals relies on combining orbitals. 

• Anti-Bonding Molecular Orbitals: These orbitals are opposite of Bonding Molecular Orbitals. They generate even more energy than the atomic orbitals. However, they are usually in an unstable state. 

Hybrid orbitals

• sp hybrid orbitals: These are the most basic form of orbitals; they are formed after combining one ‘s’ orbital and one ‘p’ orbital. They’ve linear arrangement or say they’re situated 180 degrees from the equator.  
• sp2 & sp3 hybrid orbitals: sp2 and sp3 orbitals can be termed variants of sp hybrid orbitals. These orbitals have the same number of ‘s’ orbitals as sp hybrid orbitals have (one). The difference arises due to ‘p’ orbitals. sp2 hybrid orbitals have two ‘p’ orbitals, and sp3 has three. Moreover, sp2 has a Trigonal planar shape, and sp3 has a tetrahedral shape. 
• sp3d & sp3d2 hybrid orbitals: Another two-hybrid orbital class is sp3 hybrid orbitals with additional d orbitals. sp3d orbitals have one extra ‘d’, whereas sp3d2 have two. Sp3d is in Trigonal bi-pyramidal shape. At the same time, sp3d2 orbitals have an octahedral shape. 

Molecular Orbitals and Hybrid Orbitals

Conclusion

We learned various aspects of Molecular and Hybrid orbitals from all the above. We concluded that the key difference between Molecular and Hybridisation orbitals lies in their place of combining orbitals. In Molecular orbitals, the orbitals of two different atoms merge to form new orbitals. In contrast, Hybrid orbitals are developed from the orbitals of the same atom itself. Apart from this, subtypes of molecular orbitals are bonding, Anti-Bonding Molecular orbitals and Hybrid orbitals are sp, sp2, sp3, sp3d and sp3d2.