Chapter 5: Problem 6

Why is more energy required to break a sigma bond than a pi bond?

Short Answer

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Answer: Breaking a sigma bond requires more energy than breaking a pi bond due to the nature and position of the electron cloud in these bonds. Sigma bonds have a more direct and concentrated overlap of atomic orbitals, resulting in stronger, more stable bonds. Pi bonds have a less direct overlap and their electron cloud is distributed above and below the plane of the nuclei, leading to weaker bonds. Consequently, more energy is needed to break a sigma bond compared to a pi bond.

Step by step solution

Understand Sigma and Pi Bonds

A sigma (σ) bond is a single covalent bond formed through the direct overlap of atomic orbitals (usually s and px orbitals) between two atoms. This overlap results in the sharing of electron pairs, creating a strong bond. In contrast, a pi (π) bond is formed by the parallel overlap of two p orbitals along their nodal planes. The electron cloud in a π bond is located above and below the plane of the nucleus of the bonding atoms, resulting in a weaker bond.

Compare Bond Energy between Sigma and Pi Bonds

Bond energy is the amount of energy required to break a bond between two atoms. It is an indicator of bond strength. A higher bond energy means a stronger bond, whereas a lower bond energy means a weaker bond. The energy required to break a sigma bond is generally higher than that required to break a pi bond. This is due to the nature and position of the electron cloud in these bonds.

Analyze the Electron Cloud in Sigma and Pi Bonds

In a sigma bond, the electron cloud is more concentrated between the nuclei, and there is a direct overlap of bonding orbitals. This creates a tighter, stronger bond between the atoms. In a pi bond, the electron cloud is distributed above and below the plane of the nuclei, and the orbital overlap is not as direct or concentrated. This leads to a relatively weaker bond than the sigma bond.

Consider the Stability of Sigma and Pi Bonds

Sigma bonds are more stable than pi bonds because they can survive rotations around the bond axis without breaking. The direct overlap between the bonding orbitals in sigma bonds allows for this stability. Meanwhile, pi bonds cannot survive rotations as easily, making them more susceptible to bond breakage.

Conclude

The reason more energy is required to break a sigma bond than a pi bond is due to the nature and position of the electron cloud in these bonds. Since sigma bonds have a more direct and concentrated overlap of atomic orbitals than pi bonds, they form stronger, more stable bonds. As a result, breaking a sigma bond requires more energy compared to a pi bond.

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Why is more energy required to break a sigma bond than a pi bond?

Short Answer

Step by step solution

Understand Sigma and Pi Bonds

Compare Bond Energy between Sigma and Pi Bonds

Analyze the Electron Cloud in Sigma and Pi Bonds

Consider the Stability of Sigma and Pi Bonds

Conclude

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