Question

Give resonance structure(s) for the hydroxide ion \([\mathrm{OH}]^{-} .\) What description of the bonding in this ion does valence bond theory give?

Short answer

\([ ext{OH}]^-\) has one resonance structure. Valence bond theory describes its bond with \( sp^3 \) hybridization and lone pairs on oxygen.

Step-by-step solution

Draw the Lewis Structure

The hydroxide ion \([ ext{OH}]^-\) consists of an oxygen atom bonded to a hydrogen atom, with an additional electron giving it a negative charge. To draw its Lewis structure: Oxygen (from group 16) has 6 valence electrons, and hydrogen has 1 valence electron. The additional electron (due to the negative charge) is added to oxygen. Thus, the structure is: \[:\overset{..}{O}:\text{---}\overset{..}{H}\] with the negative charge on oxygen.

Consider Possible Resonance Structures

Resonance structures are possible when there is more than one valid way to distribute the electrons around the atoms, typically involving double bonds or lone pairs. However, for \([ ext{OH}]^-\), there is only one valid arrangement of atoms without shifting those electrons to other bonds. Thus, the hydroxide ion has a single resonance structure.

Understanding Valence Bond Theory

According to Valence Bond Theory, the bonding in the hydroxide ion can be described as the overlap of orbitals. The \( \text{O} \) atom uses its \( sp^3 \) hybridized orbitals, one of which overlaps with the \( s \) orbital of hydrogen to form a sigma bond. The extra electron is accommodated as a lone pair on the oxygen atom, contributing to the ion's charge.

Key concepts

Hydroxide Ion

The hydroxide ion, denoted as \([ ext{OH}]^-\), is an important chemical entity consisting of one oxygen atom bonded to one hydrogen atom. It bears a negative charge due to the presence of an extra electron. This negative charge gives the hydroxide ion its characteristic properties and reactivity. Understanding the hydroxide ion is crucial as it commonly appears in various chemical reactions, especially in acid-base chemistry.

• The extra electron results in a complete octet for oxygen, making it more stable.
• It acts as a base, meaning it can accept protons (H^+).
• Key player in reactions such as neutralization, where it combines with protons to form water.

Recognizing the basic structure and behavior of the hydroxide ion can greatly aid in grasping broader chemical concepts.

Lewis Structure

A Lewis structure is a simple way to represent the electron arrangement in molecules and ions. For the hydroxide ion, this structure depicts the bonds between the atoms and the lone pairs of electrons, providing a visual representation of the molecule's electron distribution.

• Oxygen, part of group 16 in the periodic table, has 6 valence electrons.
• Hydrogen contributes 1 valence electron.
• Due to the negative charge, an additional electron is added, giving the hydroxide ion a total of 8 electrons.

To draw the Lewis structure for the hydroxide ion: 1. Place the electrons around the oxygen to satisfy the octet rule. 2. Bond the lone hydrogen atom with oxygen via one of oxygen's available orbitals. 3. Represent lone pair electrons on oxygen for full electron accounting. The resulting structure shows an oxygen atom bonded to a hydrogen atom with three lone pairs on oxygen, highlighting its reactivity and stability.

Valence Bond Theory

Valence Bond Theory offers a detailed explanation of how atoms connect to form molecules, emphasizing the overlap of atomic orbitals. In the case of the hydroxide ion, this theory helps explain the nature of the bond between oxygen and hydrogen.

• Oxygen is typically \(sp^3\) hybridized, meaning it forms four equivalent orbitals.
• One \(sp^3\) orbital overlaps with hydrogen's \(s\) orbital, creating a sigma bond.
• The remaining \(sp^3\) orbitals accommodate the lone pairs and the additional electron, balancing the charge and contributing to the ion's overall stability.

This overlap and hybridization are key to understanding molecular structure and reactivity, showing how the arrangement of orbitals and electrons influences chemical behavior.

Resonance Structures

Resonance structures are a concept used in chemistry to illustrate molecules or ions that cannot be represented by a single Lewis structure. They are alternative representations that account for the possible distribution of electrons. However, the hydroxide ion is unique in that it only has a single valid Lewis structure.Due to its simplicity and the way its electrons are arranged, there are no alternate structures for \([ ext{OH}]^-\) that maintain its stability and satisfy chemical rules. Generally,

• Resonance structures usually occur in more complex ions or molecules where electrons can be delocalized across multiple bonds.
• The hydroxide ion's electrons are constrained to a singular configuration without feasible alternatives.

Understanding why the hydroxide ion lacks resonance structures highlights the limitations of electron distribution in simpler ions, contrasting with the behavior of larger, more complex species.