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2 Models of Bonding and Structure

Introduction to Bonding

  • Different ways atoms combine to form compounds: ionic, covalent, and metallic bonding.

  • Chemical bonds lead to distinct physical and chemical properties of substances.

Bonding Models

Overview

  • Bonds result from how atoms share or transfer electrons.

  • Models of bonding help explain reactivity, stability, and physical properties of materials.

Computer Graphic Representation

  • Illustration of zeolite-Y structure.

    • Silicon (Si) and Aluminum (Al) in yellow; Oxygen (O) in red.

    • Zeolite structure's open caged properties provide it excellent catalytic properties.

  • All substances formed from combinations of just over 100 different atomic types.

    • Variety in the material world revolves around different ways atoms can bond and combine.

Chemical Bonds

Simple Bonds

Ionic Bonds

  • Formed through the transfer of electrons, resulting in oppositely charged ions.

    • Example: NaCl (sodium chloride).

Covalent Bonds

  • Formed through sharing electrons.

    • Bonds can be single, double, or triple (single = sigma bond, double = sigma + pi bond).

Metallic Bonds

  • Involves a sea of delocalized electrons surrounding positively charged cations.

  • Results in high conductivity of electrical current and heat.

Ionic Bonding

Ionic Model

  • Insulin molecule, a significant protein, illustrated with ball-and-stick models showing structure.

  • Ionic Compounds: M + X = M+ + X-

  • Characteristics:

    • Crystalline structures.

    • Exhibits specific properties due to lattice structure.

Predictions and Properties

  • Trends in periodic table can predict ionic charge and bonding behavior.

Covalent Bonds

Covalent Properties

  • Properties based on the nature of shared electrons and molecular shape.

  • Formal Charge applied to predict stable Lewis structures.

    • Helps differentiate between multiple resonance structures.

Hybridization

Explanation

  • Hybridization is the process where atomic orbitals mix to create new orbitals for bonding.

  • Types include: sp, sp2, and sp3 depending on the number of electron domains.

Geometry and Hybridization

  • Shapes predicted based on hybridization:

    • sp: linear

    • sp2: triangular planar

    • sp3: tetrahedral

Intermolecular Forces

Types of Intermolecular Forces

  • London Dispersion Forces: present in non-polar molecules; weakest.

  • Dipole-Dipole Forces: present in polar molecules; stronger than London forces.

  • Hydrogen Bonds: strong interaction occurring between hydrogen bonded to highly electronegative atoms.

  • The arrangements and strength of these forces govern properties like boiling point and solubility.

Polymerization

Addition vs. Condensation Polymers

Addition Polymers

  • Formed by breaking double bonds and linking monomers without releasing small molecules.

    • Example: Polyethylene from ethylene.

Condensation Polymers

  • Formed by connecting monomers via the reaction of functional groups with the loss of water.

    • Example: Nylon from carboxylic acids and amines.

Summary of Bonding Models

  • Electrical conductivity, thermal conductivity, malleability explained through bonding types.

  • Metals show distinct properties due to delocalized electrons contributing to their bonding structure.

Conclusion

  • Understanding the interplay between bond types and molecular structure enhances material design and application across industries.