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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.