Atomic Orbital Overlap, s-s Overlap, s-p Overlap, p-p Overlap with Diagrams

Priyanka Waghmare | Updated: Dec 27, 2021 21:11 IST

Atomic orbital overlaps are seen in covalent bonding. The atomic orbitals overlap to form new shapes. In this article, we are going to study the three atomic orbital overlaps s-s Overlap, s-p Overlap, p-p Overlap with Definition, Structure, Explanation and Diagrams

What is Atomic Orbital Overlap?

When two atoms combine together to form a covalent bond, their energy is minimum when they are so close to each other that their orbitals are partially merged. This partial merging of atomic orbitals is known as orbital overlapping or overlapping of atomic orbitals.

There are two types of overlapping orbitals: sigma (σ ) and pi (π ). Both bonds are formed from the overlap of two orbitals, one on each atom. σ bonds occur when orbitals overlap between the nuclei of two atoms, also known as the internuclear axis.

Thus atoms form a lower energy state where their valence electrons with opposite spin, pair up to form a covalent bond.

Leran about Haloalkanes here.

Types of Overlap of Atomic Orbitals

During the formation of a single covalent bond, involving s and p orbitals three different types of orbital overlaps are possible.

s-s overlap: (Formation of \(H_2\) molecule)

The overlap between two half-filled s-orbitals of two different atoms containing unpaired with opposite spins is called s-s overlap.

For example formation of \(H_2\) molecule :

The electronic configuration of the hydrogen atom is \(1s^1\) .

During the formation of H, molecule, half-filled 1s – orbital of one hydrogen atom that contains the unpaired the electron overlaps with half-filled is orbital of another hydrogen atom having electrons with opposite spin. Such an overlap is called s-s overlap and the bond formed is the s-s sigma bond. The bond is formed by the axial overlap of orbitals hence it is a sigma \((\sigma)\) bond.

p-p overlap: (Formation of halogen (\(F_2\) ) molecule.)

The overlap between two half-filled p orbitals of two different atoms containing electrons with opposite spins is called p-p overlap. e.g. (Formation of \(F_2\) molecule)

The electronic configuration of fluorine atom (Z = 9) is \(1s^2, 2s^2, 2p_x^2, 2p_y^2,2p_z^1\)

During the formation of \(F_2\) molecule, half-filled \(2p_z\), orbital of one 'F' atom overlaps with similar half-filled \(2p_z\), orbital containing electron with opposite spin, of another F atom co-axially and a p-p covalent sigma bond is formed.

'p' orbitals have a dumb-bell shape and hence overlap takes place in a particular direction. Therefore the p-p bond has a directional character. When p orbital takes part in overlap another lobe of p orbital gets reduced in size i.e. shrinks.

s-p overlap (Formation of HF molecule)

The overlap between one half-filled s orbital of one atom and one half-filled p orbital of another atom containing electrons with opposite spins is called S-p overlap. e.g. Formation of HF molecule

The electronic configuration of H atom (Z = 1) is Is' and that of fluorine atom (Z = 9) is \(1s^2, 2s^2, 2p_x^2, 2p_y^2,2p_z^1\)

During the formation of HF molecule, half-filled ls orbital of hydrogen atom overlaps coaxially with half-filled \(2p_z\), orbital of fluorine atom-containing electron with opposite spin and an s-p covalent bond is formed. It is a sigma bond since the overlap of atomic orbitals is axial.

HF is a polar molecule

In the case of the HF molecule, the bond is formed between two dissimilar atoms. F is highly electronegative and its electronegativity is 4. The electronegativity of hydrogen is 2.1. The shared pair of electrons gets shifted more towards the fluorine atom. Hence F atom acquires a partial negative charge and the hydrogen atom acquires a partial positive charge. The bond becomes polar due to large differences in electronegativities. Hence HF is a polar molecule and H-F bond is a polar covalent bond.

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Atomic Orbital Overlap FAQs

Q.1 What type of atomic orbitals overlap?

Ans.1 There are two types of overlapping orbitals: sigma (σ ) and pi (π ). Both bonds are formed from the overlap of two orbitals, one on each atom. σ bonds occur when orbitals overlap between the nuclei of two atoms, also known as the internuclear axis.

Q.2 What happens when electron orbitals overlap?

Ans.2 Orbital overlap begins to occur, as the electron orbitals move closer and closer together. This lowers the potential energy of the system, as new, attractive positive-negative electrostatic interactions become possible between the nucleus of one atom and the electron of the second. This leads to the formation of the bands.

Q.3 What is overlap integral?

Ans.3 The Overlap Integral is a quantitative measure of the overlap of atomic orbitals situated on different atoms. The overlap of the atomic orbital of an atom A and the atomic orbital of an atom B is called their overlap integral.

Q.4 What is PP orbital overlapping?

Ans.4 The overlap between two half-filled p orbitals of two different atoms containing electrons with opposite spins is called p-p overlap. e.g. (Formation of \(F_2\) molecule). The mutual overlap between two half-filled p-orbitals of two atoms is called p-p overlap. So the covalent bond formed is called a p-p bond. The formation of such a bond is also called axial overlapping. The two 'p' orbitals overlap each other when they acquire minimum potential energy.

Q.5 Which bond is stronger SS or SP?

Ans.5 S-S overlap is stronger than s-p, p-p and p-d overlap. This is due to the similar size and high electronegativity of s orbitals which make the overlap stronger.

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