Chapter 24: Problem 12
Abnormality high heat of formation and shortening of bond length are criteria of (a) hybridisation (b) resonance (c) electron delocalisation (d) ionization
Short Answer
Expert verified
The correct option is (c) electron delocalisation.
Step by step solution
01
Understand Key Concepts
First, identify what each option (a, b, c, d) means. Hybridisation is the mixing of atomic orbitals in an atom. Resonance refers to the concept of delocalized electrons within molecules where bonds can't be described by a single Lewis structure. Electron delocalisation is related to the distribution of electrons across several atoms. Ionization involves removing an electron from an atom or molecule.
02
Review Heat of Formation and Bond Length
Abnormal heat of formation indicates a very stable or unstable structure compared to the average expected stability. Short bond lengths typically suggest stronger bonds. Both conditions suggest enhanced stability or bond strength in the structure.
03
Relate Concepts to Observations
Hybridisation affects the shape and energy levels but doesn't directly result in abnormality of heat of formation or bond length. Ionization doesn't typically relate to bond lengths in stable molecules. Delocalisation of electrons, however, is known to influence energy stability and bond lengths, consistent with the observations.
04
Validate Resonance Efficacy
Electron delocalisation often arises from resonance, where electrons are not localized but distributed over several atoms. This electron sharing leads to bonding characteristics that fit the given abnormality in bond lengths and formation heats.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Electron Delocalization
Electron delocalization is a fascinating concept in chemistry. It refers to the distribution of electrons across several atoms within a molecule, rather than being confined to a single atom or bond. This usually occurs in systems that have conjugated pi bonds, such as benzene.
Delocalization brings increased stability to a molecule because the electrons are "spread out" over a larger area, lowering the overall energy. This stability is a crucial factor in the heat of formation, making delocalized systems typically more stable than localized ones. For students, understanding delocalization helps in predicting molecular behavior and properties like conductivity and chemical reactivity.
Delocalization brings increased stability to a molecule because the electrons are "spread out" over a larger area, lowering the overall energy. This stability is a crucial factor in the heat of formation, making delocalized systems typically more stable than localized ones. For students, understanding delocalization helps in predicting molecular behavior and properties like conductivity and chemical reactivity.
Heat of Formation
The heat of formation is the change in energy when one mole of a compound is formed from its elements in their standard states. This concept gives us insight into the stability of a compound.
An abnormally high heat of formation indicates an unusually stable compound, where energy is released when the compound forms. This often results from strong bonds or, in the context of the exercise problem, electron delocalization.
When electrons are delocalized within a molecule, they contribute to the molecule's stability, often leading to a high heat of formation, since the molecule releases a lot of energy to reach a stable state.
An abnormally high heat of formation indicates an unusually stable compound, where energy is released when the compound forms. This often results from strong bonds or, in the context of the exercise problem, electron delocalization.
When electrons are delocalized within a molecule, they contribute to the molecule's stability, often leading to a high heat of formation, since the molecule releases a lot of energy to reach a stable state.
Bond Length
Bond length is the average distance between the nuclei of two bonded atoms. It is a critical factor determining the strength and characteristics of the bond.
Shorter bond lengths typically indicate stronger bonds, as the bonded atoms are closer together. This usually results from effective electron sharing or delocalization, which explains the impact of electron delocalization on bond length.
In resonance-stabilized systems, bond lengths can be shorter due to the electrons being shared across several atoms, making the bonds "partial" and stronger. Understanding bond lengths helps us predict molecular shapes and bonding patterns.
Shorter bond lengths typically indicate stronger bonds, as the bonded atoms are closer together. This usually results from effective electron sharing or delocalization, which explains the impact of electron delocalization on bond length.
In resonance-stabilized systems, bond lengths can be shorter due to the electrons being shared across several atoms, making the bonds "partial" and stronger. Understanding bond lengths helps us predict molecular shapes and bonding patterns.
Hybridization
Hybridization is the process where atomic orbitals combine to form new hybrid orbitals, which can help explain molecular geometry.
It affects the shape and orientation of molecules, influencing how atoms are arranged in a structure. Hybridization levels (sp, sp2, sp3) dictate the number and type of bonds that can form, impacting angles and orientation.
While hybridization is vital in understanding molecular shapes, it does not have a direct effect on heat of formation or bond lengths in the context of resonance or electron delocalization. Recognizing this can help students distinguish between geometric and energy-related properties.
It affects the shape and orientation of molecules, influencing how atoms are arranged in a structure. Hybridization levels (sp, sp2, sp3) dictate the number and type of bonds that can form, impacting angles and orientation.
While hybridization is vital in understanding molecular shapes, it does not have a direct effect on heat of formation or bond lengths in the context of resonance or electron delocalization. Recognizing this can help students distinguish between geometric and energy-related properties.
Ionization
Ionization is the process of removing an electron from an atom or molecule, which results in a positive charge. It requires energy to overcome the attraction between the negatively charged electrons and the positively charged nucleus.
This concept is essential for understanding reactions in chemistry, especially those involving the formation of ions in solution or gas phase.
However, ionization doesn't typically have a direct role in influencing bond length or formation heat in stable molecules. In the context of the given problem, it's important to differentiate this process from electron delocalization and resonance, which have a more significant impact on stabilizing molecules and affecting their bond lengths.
This concept is essential for understanding reactions in chemistry, especially those involving the formation of ions in solution or gas phase.
However, ionization doesn't typically have a direct role in influencing bond length or formation heat in stable molecules. In the context of the given problem, it's important to differentiate this process from electron delocalization and resonance, which have a more significant impact on stabilizing molecules and affecting their bond lengths.
