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Ch.22 - The Main Group Elements
Chapter 22, Problem 49

Carbon, nitrogen, and oxygen form π bonds, but fluorine does not. Explain.

Verified step by step guidance
1
Step 1: Understand the concept of π bonds. π bonds are formed by the sideways overlap of p orbitals. They are typically found in double and triple bonds, where one of the bonds is a σ bond and the others are π bonds.
Step 2: Consider the atomic size and electronegativity. Carbon, nitrogen, and oxygen have relatively small atomic sizes and moderate electronegativity, allowing their p orbitals to overlap effectively to form π bonds.
Step 3: Analyze the case of fluorine. Fluorine is highly electronegative and has a small atomic size, which leads to a strong attraction for its own electrons, making it less likely to share electrons through π bonding.
Step 4: Examine the electron configuration. Fluorine's electron configuration ends in 2p^5, meaning it has one unpaired electron in the p orbital, which is more likely to form a σ bond rather than a π bond due to its high electronegativity.
Step 5: Conclude with the stability of π bonds. The formation of π bonds requires effective overlap and sharing of electrons, which is less favorable for fluorine due to its high electronegativity and tendency to hold onto its electrons tightly, thus preferring σ bonds.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

π Bonds

π bonds are a type of covalent bond formed when two lobes of one involved atomic orbital overlap with two lobes of another, typically occurring in double and triple bonds. They arise from the side-to-side overlap of p orbitals, allowing for the sharing of electrons between atoms. Carbon, nitrogen, and oxygen can form π bonds due to their ability to engage in hybridization and have available p orbitals.
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Hybridization

Hybridization is the concept of mixing atomic orbitals to create new hybrid orbitals that can form bonds with other atoms. For example, carbon can undergo sp² or sp³ hybridization, allowing it to form multiple bonds, including π bonds. Nitrogen and oxygen also participate in hybridization, enabling them to form stable π bonds in their molecular structures.
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Fluorine's Electron Configuration

Fluorine has an electron configuration of 1s² 2s² 2p⁵, which means it has only one unpaired electron in its 2p orbital. This configuration limits its ability to form π bonds, as it prefers to form single bonds through σ bonding by sharing its unpaired electron. Additionally, fluorine's high electronegativity and small size make it less likely to engage in the types of bonding that involve π interactions.
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