Sigma and Pi Bonds in Covalent Bonding
Introduction to Covalent Bonds
Covalent bonds are formed by the sharing of electrons between atoms. Sigma (σ ) and Pi (π ) bonds are two
types of covalent bonds that differ in how atomic orbitals overlap.
Sigma (σ ) Bonds
Formation: Sigma bonds are formed by the head-to-head (linear) overlap of atomic orbitals. This
overlap occurs along the internuclear axis.
Orbitals Involved:
Overlap between two s orbitals.
Overlap between an s orbital and a p orbital.
Overlap between two p orbitals along their axis.
Characteristics:
Sigma bonds are strong bonds and are not easily broken.
A single covalent bond is always a sigma bond.
Examples:
Hydrogen molecule (H2 ): The bond is formed by the overlap of two 1s orbitals, resulting in a
sigma bond.
Methane (CH4 ): All four C-H bonds are sigma bonds.
Ethane (C2 H6 ): All bonds in ethane are single bonds, and therefore all are sigma bonds.
Pi (π ) Bonds
Formation: Pi bonds are formed by the side-to-side (lateral) overlap of atomic orbitals. This overlap
occurs above and below the internuclear axis.
Orbitals Involved:
Overlap of two parallel p orbitals.
Characteristics:
Pi bonds are weaker than sigma bonds because the overlap is less effective.
Pi bonds are more easily broken than sigma bonds.
Pi bonds are only found in double and triple bonds.
Occurrence:
Double bonds consist of one sigma bond and one pi bond.
Triple bonds consist of one sigma bond and two pi bonds.
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Introduction to Covalent Bonds
Covalent bonds are formed by the sharing of electrons between atoms. Sigma (σ ) and Pi (π ) bonds are two
types of covalent bonds that differ in how atomic orbitals overlap.
Sigma (σ ) Bonds
Formation: Sigma bonds are formed by the head-to-head (linear) overlap of atomic orbitals. This
overlap occurs along the internuclear axis.
Orbitals Involved:
Overlap between two s orbitals.
Overlap between an s orbital and a p orbital.
Overlap between two p orbitals along their axis.
Characteristics:
Sigma bonds are strong bonds and are not easily broken.
A single covalent bond is always a sigma bond.
Examples:
Hydrogen molecule (H2 ): The bond is formed by the overlap of two 1s orbitals, resulting in a
sigma bond.
Methane (CH4 ): All four C-H bonds are sigma bonds.
Ethane (C2 H6 ): All bonds in ethane are single bonds, and therefore all are sigma bonds.
Pi (π ) Bonds
Formation: Pi bonds are formed by the side-to-side (lateral) overlap of atomic orbitals. This overlap
occurs above and below the internuclear axis.
Orbitals Involved:
Overlap of two parallel p orbitals.
Characteristics:
Pi bonds are weaker than sigma bonds because the overlap is less effective.
Pi bonds are more easily broken than sigma bonds.
Pi bonds are only found in double and triple bonds.
Occurrence:
Double bonds consist of one sigma bond and one pi bond.
Triple bonds consist of one sigma bond and two pi bonds.
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