Summary of Ionic and Covalent Bonding and Nomenclature (4.1-4.3 Lecture 9)

Ionic Bonds

  • Definition: Bond formed between a metal and a nonmetal, specifically between a cation (positive ion) and an anion (negative ion).

Types of Chemical Bonds

  • Ionic Bond: Involves formation between a cation and an anion.

  • Covalent Bond: Occurs between two or more nonmetals where atoms SHARE electrons.

Ionic Compounds and Ions

  1. Ions: Charged particles that can be formed when atoms gain or lose electrons.

    • Cations: Positive ions formed by losing electrons.

    • Anions: Negative ions formed by gaining electrons.

Ionic Bonding Principles

  • Goal of Main Group Elements: Achieve a full octet in their outermost shell.

    • Metals lose electrons, while nonmetals gain electrons to attain a full shell.

Energies Involved in Ionic Bonding

  • 1st Ionization Energy of Na: +496 kJ/mol (endothermic)

  • Electron Affinity of Cl: -349 kJ/mol (exothermic)

  • Combined Energy Change: 496 kJ/mol + (-349 kJ/mol) = +147 kJ/mol (indicates the reaction is endothermic and non-spontaneous).

  • Lattice Energy: Energy associated with forming a crystal lattice from gaseous ions, determining the stability of ionic compounds.

Properties of Ionic Compounds

  • Most ionic compounds form crystals due to the electrostatic attraction between the cations and anions.

Covalent Compounds

  • Definition: Involves sharing of electrons between atoms.

  • Common Example: Methane (CH4)

    • Molecular Formula: Shows quantity of atoms.

    • Structural Formula: Illustrates exact connectivity of the atoms.

    • Ball-and-Stick Model: Visual representation showing atoms as balls and bonds as sticks.

    • Space-Filling Model: Displays the electron cloud around atoms.

Ways to Represent Molecules

  1. Molecular Formula: Total number of atoms, no structural information included.

    • Order of representation: C, H, then other elements (CHBrClFNOPS for organic).

  2. Condensed Formula: Shows number of atoms and structure cues for connectivity.

  3. Structural Formula: Shows exact connectivity using symbols and lines for bonds.

  4. Molecular Model: Uses colored balls and sticks.

  5. Space-Filling Model: Utilizes atomic radii to illustrate electron clouds.

Lewis Structures

  • Purpose: Illustrate where electrons in bonds originate.

    • Lewis dot symbols used to show valence electrons.

    • Example: Oxygen and its paired/unpaired electrons.

    • Shared bonding electrons depicted as lines in diagrams.

Double and Triple Bonds

  • Involves Lewis Structures where two or three pairs of electrons are shared between atoms.

Naming Ionic Compounds

  • Requires memorization of specific tables for accurate nomenclature (e.g., tables 4.2, 4.3, and 4.4 in referenced material).

  • Important Note: Transition metals can have multiple charges; the charge must be specified.

    • Anion charge can help determine the metal's charge.

Charge of Common Ions

  • Common Cations:

    • Li+, Be²+, Na+, K+, Ca²+, etc.

  • Transition Metals: Fe2+ (Iron(II), Ferrous), Fe3+ (Iron(III), Ferric), etc.

Polyatomic Ions Example Table

  • Common Ion Names:

    • Ammonium (NH₄⁺), Acetate (C₂H₃O₂⁻), Carbonate (CO₃²⁻), etc.

Naming Hydrated Ionic Compounds

  • Naming adjusted based on whether water of hydration is present, e.g., Co(II)Cl₂·6H₂O.

Simple Covalent Compound Naming

  • Utilize prefixes to denote the number of atoms:

    • Mono-, Di-, Tri-, Tetra-, Penta-, Hexa-, Hepta-, Octa-, Nona-, Deca-.

  • Example of naming covalent compounds: CO₂ is Carbon Dioxide.

Summary

  • Understanding ionic and covalent bonds, molecular representations, and the rules of naming ionic and covalent compounds are fundamental to mastering chemistry concepts related to chemical bonds.