s-s Overlapping

Valence Bond Theory:

The overlap of half-filled atomic orbitals (each holding a single electron) yields a pair of electrons shared between the two linked atoms, according to the Valence Bond Theory. When a part of one orbital and a part of a second orbital occupies the same area of space on two separate atoms, we say they overlap.

A covalent bond is formed when two requirements are met: 

(1) an orbital on one atom overlaps an orbital on another atom, and 

(2) the isolated electrons in each orbital unite to create an electron pair, according to valence bond theory. 

The mutual interaction between this negatively charged electron pair and the positively charged nuclei of the two atoms creates a covalent bond that physically connects the two atoms. 

The level of overlap of the orbitals involved determines the strength of a covalent bond. Orbitals with a lot of overlap form stronger bonds than orbitals with less overlap.

Hybridisation

Hybridisation is defined as the combining of atomic orbitals belonging to the same atom but with slightly varying energies, resulting in an energy redistribution between them and the production of new orbitals with equal energies and identical shapes.

Hybrid orbitals are the new orbitals created in this way.

Atoms can create bonds by sharing unpaired electrons, resulting in two electrons in each link. 

For example: When a carbon atom establishes bonds and becomes a member of a molecule structure, the s and p orbitals of its second shell might be ‘mixed’ (the valence shell). This is called hybridization, and it is what allows carbon to create the four bonds that we see in reality.

This can happen in three different ways:

• All three orbitals are combined with the orbital. Hybridisation is the term for this.

• Two of the orbitals are mixed together with the orbital. Hybridisation is the term for this.

• One of the two orbitals is merged with the orbital. Hybridisation between species is called as hybridization.

Rules for hybridisation:

• In isolated atoms, hybrid orbitals do not exist. 

• Only covalently bound atoms can generate them.

• The orientation of hybrid orbitals is different from that of atomic orbitals.

• The combination of atomic orbitals leads to the formation of the hybrid orbital. The number of atomic orbitals required is the same as the number of molecular orbitals formed.

• According to the VSEPR theory, the electron pair geometry is responsible for the determination of the type of hybrid orbitals created.

• Bonds are formed when hybrid orbitals overlap. Bonds are formed when unhybridized orbitals collide.

Hydrogen molecule formation:

The electronic configuration of hydrogen is :

The orbitals of two hydrogen atoms carrying one unpaired electron with opposing spin interact with each other along the inter – atomic axis during the creation of the molecule. This type of overlap is known as overlap. The creation of a –covalent bond is the outcome of such axial overlap.

Conclusion:

The overlap of two independent atomic orbitals on different atoms provides an area with one pair of electrons shared by the two atoms, according to the Valence Bond Theory.

 A bond is formed when the orbitals overlap along an axis that contains the nuclei. They establish a bond when they overlap in a way that generates a node along this axis.