The bond formed by the sharing of electrons is called covalent bond. Here, we will discuss its types.
Types of Covalent bond
Covalent bonds are of 2 types depending upon covalent bonding.
Sigma bond
The overlapping of atomic orbitals along the internuclear axis results in the formation of sigma bond. This is head on or end to end overlap. It has 3 types.
a) s-s overlapping
The overlapping takes place between the atoms having half filled s orbitals. For example : H2 molecule. 1s orbital overlaps with 1s orbital to form H2 molecule. Similarly, s-s overlapping occurs in case of Li2 molecule.
b) s-p overlapping
The overlapping takes place between half-filled s orbital of one atom and half-filled p orbital of another atom. The example of s-p overlapping includes formation of HF.
c) p-p overlapping
The overlapping takes place between the half filled p orbitals of 2 atoms. For example in F2, Cl2 etc.
Pi bond
The sidewise overlapping of atomic orbitals results in the formation of pi bond. For example in CH2=CH2 molecule 1 pi bond is present.
Comparison of sigma and Pi covalent bond
- Sigma bond forms by the end to end or overlapping along internuclear axis. Pi bond forms by the lateral overlapping of atomic orbitals.
- Overlapping occurs between s-s, s-p and p-p atomic orbitals in case of sigma bonding. Pi bonding forms by the overlapping of p-p orbitals only.
- The overlapping is large in case of sigma bon in comparison to pi bond.
- Electron cloud is symmetrical in case of sigma bond but unsymmertrical in case of pi bond
- Free rotation is possible in sigma bonding. In case of pi bond, free rotation is not possible. Because on rotation the bond breaks.
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