Question:

What is the total number of sigma and pi bonds in the following molecules?
  1. \(C_2H_2\) 
  2. \(C_2H_4\)

Updated On: Nov 10, 2023
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Solution and Explanation

a. A single bond is a result of the axial overlap of bonding orbitals. Hence, it contributes a sigma bond. A multiple bond (double or triple bond) is always formed as a result of the sidewise overlap of orbitals. A \(pi-bond\) is always present in it. A triple bond is a combination of two \(pi-bonds\) and one \(sigma \;bond\).
Structure of \(C_2H_2\) can be represented as:
Structure of C2H2
Hence, there are three sigma and two \(pi-bonds\) in \(C_2H_2\)


The structure of \(C_2H_4\) can be represented as:
The structure of C2H4
Hence, there are five sigma bonds and one \(pi-bond\) in \(C_2H_4\).

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Concepts Used:

Chemical Bonding and Molecular Structure

Such a group of atoms is called a molecule. Obviously, there must be some force that holds these constituent atoms together in the molecules. The attractive force which holds various constituents (atoms, ions, etc.) together in different chemical species is called a chemical bond.

Types of Chemical Bonds:

There are 4 types of chemical bonds which are formed by atoms or molecules to yield compounds. 

  • Ionic Bonds - Ionic bonding is a type of chemical bonding which involves a transfer of electrons from one atom or molecule to another.
  • Covalent Bonds - Compounds that contain carbon commonly exhibit this type of chemical bonding. 
  • Hydrogen Bonds -  It is a type of polar covalent bonding between oxygen and hydrogen wherein the hydrogen develops a partial positive charge
  • Polar Bonds - In Polar Covalent chemical bonding, electrons are shared unequally since the more electronegative atom pulls the electron pair closer to itself and away from the less electronegative atom.

Factors Affecting Bond Enthalpy in Chemical Bonding:

  • Size of the Atom
  • Multiplicity of Bonds
  • Number of Lone Pair of Electrons Present
  • Bond Angle