Chapter 8: Problem 60
How is the concept of resonance consistent with the octet rule?
Short Answer
Expert verified
Resonance is consistent with the octet rule because it allows atoms in a molecule to share electrons in a way that each atom achieves a stable configuration (usually an octet). This is done through representing the molecule with multiple 'resonance structures' which each contribute to the overall electron structure of the molecule, adhering to the most stable state usually portrayed by the octet rule.
Step by step solution
01
Understanding Resonance
Resonance in chemistry is a way of describing delocalized electrons within certain molecules or polyatomic ions where the connectivity cannot be expressed by a single Lewis structure. It is, rather, a combination of several Lewis structures.
02
Understanding the Octet Rule
The octet rule is a chemical rule of thumb that reflects the theory that atoms of main-group elements tend to combine in such a way that each atom has eight electrons in its valence shell, equivalent to the electron configuration of a noble gas.
03
Connection between Resonance and the Octet Rule
Resonance structures allow us to represent the delocalized electrons that form part of an atom's stable arrangements (as described by the octet rule). Various atoms can share their electrons with each other to complete their octet, leading to the state where they hold the most stable electron configuration. The multiple resonance structures are representations of the molecule’s electron distribution, and each contributes to the overall electron structure, adhering to the most stable state, often portrayed by the octet rule. This is hence consistent with the concept of the octet rule - as resonance aims to depict the delocalized electrons across the molecule, for a more unified, stable state where atoms try to reach the most stable electron configuration, fulfilling the eight electron condition in the outer shell where possible.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Lewis Structures
Lewis structures serve as a visual representation of the valence electrons of atoms, showing the arrangement of these electrons in molecules. Over each atom in a Lewis structure, a group of dots or lines signifies the electrons in the valence shell—the outermost electron shell, which is significant in chemical bonding.
When drawing Lewis structures, shared electron pairs between atoms are depicted as lines (bonds), while non-bonding electrons are shown as dots. This graphical representation assists in predicting the number and types of bonds that may form between atoms in a molecule and provides a conceptual foundation for understanding chemical reactions and properties.
When drawing Lewis structures, shared electron pairs between atoms are depicted as lines (bonds), while non-bonding electrons are shown as dots. This graphical representation assists in predicting the number and types of bonds that may form between atoms in a molecule and provides a conceptual foundation for understanding chemical reactions and properties.
- Shows how atoms are bonded in a molecule.
- Represents lone pairs or non-bonding electrons.
- Helps predict molecular geometry and reactivity.
Octet Rule
The octet rule is a concept that explains the stability of most chemical compounds in terms of electron configurations. Atoms are most stable when they have a full set of electrons in their valence shell, which usually means eight electrons—akin to the electron configuration of a noble gas.
Atoms achieve this by sharing, gaining, or losing valence electrons to complete their last shell. Elements, particularly main-group ones, tend to follow this rule when they form molecules or ions:
Atoms achieve this by sharing, gaining, or losing valence electrons to complete their last shell. Elements, particularly main-group ones, tend to follow this rule when they form molecules or ions:
- Atoms can share electrons to get the desired eight, forming covalent bonds.
- Metals tend to lose electrons, while nonmetals gain, forming ionic bonds.
- Octet rule guides the creation of stable molecular structures.
Delocalized Electrons
Delocalized electrons are electrons in a molecule or ion that are not associated with a single atom or a single covalent bond. Instead, these electrons are spread over several different atoms or across pi bonds. This concept is a key part of resonance in chemistry, as it represents the electrons that can be located in different places within a molecule.
Key characteristics of delocalized electrons include:
Key characteristics of delocalized electrons include:
- They can contribute to the bonding in multiple positions in a molecule.
- They increase the stability of molecules or ions.
- Delocalization is typically represented in multiple Lewis structures.
Valence Shell
The valence shell is the outermost electron shell of an atom and plays a crucial role in chemical bonding. The electrons in the valence shell, called valence electrons, determine an atom's chemical properties and its ability to bond with other atoms. These factors are pivotal when it comes to the formation of chemical structures and the overall stability of molecules.
In essence, the valence shell is where the magic of chemistry happens. It's where:
In essence, the valence shell is where the magic of chemistry happens. It's where:
- Atoms interact and form bonds through the exchange or sharing of valence electrons.
- The octet rule applies, aiming to fill the valence shell with eight electrons.
- Electron configurations are used to predict reactivity and bonding patterns.
Noble Gas Electron Configuration
The noble gas electron configuration refers to the phenomenon where atoms have a complete set of electrons in their valence shell, resulting in extraordinary chemical stability. Noble gases like neon, argon, and helium have full outer shells, making them largely nonreactive. This configuration is often the goal for other elements during chemical bonding.
Atoms in chemical compounds often seek to achieve this naturally stable arrangement by:
Atoms in chemical compounds often seek to achieve this naturally stable arrangement by:
- Sharing electrons through covalent bonds.
- Transferring electrons in ionic bonds.
- Achieving a pseudo-noble gas electron configuration, in some transition metals, with eighteen electrons in the valence shell.
Chemical Stability
Chemical stability refers to the tendency of a chemical substance to resist changes or to decompose in reaction to environmental factors. A chemically stable molecule is one that is less likely to react with other substances or to change its structure. Chemical stability is sought after in materials for various applications, from pharmaceuticals to construction materials.
Some factors that influence chemical stability include:
Some factors that influence chemical stability include:
- Valence electrons and their arrangements, often seeking the octet configuration.
- The presence of delocalized electrons can enhance stability through resonance.
- The molecular structure, where symmetrical arrangements can lend stability.