Chemivcal Bonding and Lewis

  1. Distinguishing Ionic and Covalent Compounds

    • Ionic Compounds:

      • Formed by the transfer of electrons from metals to nonmetals, resulting in charged ions.

      • Generally have high melting and boiling points, and they conduct electricity when dissolved in water.

    • Covalent Compounds:

      • Formed by the sharing of electrons between nonmetal atoms.

      • Generally have lower melting and boiling points than ionic compounds; do not conduct electricity in solution.

  2. Rules of Nomenclature

    • Ionic Compounds:

      • Named by combining the name of the metal (cation) and the nonmetal (anion) with the anion's name ending in -ide (for simple compounds) or naming polyatomic ions.

    • Covalent Compounds:

      • Use prefixes (mono-, di-, tri-, etc.) to indicate the number of atoms; the second element name ends in -ide.

    • Oxoacids:

      • Named based on the anion: if it ends in -ate, the acid name ends with -ic; if it ends in -ite, the acid name ends with -ous.

    • Hydrates:

      • Named by indicating the number of water molecules using prefixes (e.g., monohydrate, dihydrate) followed by the compound name.

    • Simple Alkanes:

      • Named using the prefix that corresponds to the number of carbon atoms followed by the suffix -ane.

  3. Relationships Between Avogadro's Number, Moles, Molar Mass, and Grams:

    • Moles = mass (g) / molar mass (g/mol)

    • 1 mole = 6.022×10236.022 \times 10^{23} entities (Avogadro's number).

    • To calculate number of particles: # of particles = moles × 6.022×10236.022 \times 10^{23}.

  4. Distinguishing Empirical and Molecular Formulas:

    • Empirical Formula:

      • Simplest whole-number ratio of atoms in a compound.

    • Molecular Formula:

      • Actual number of atoms of each element in a compound; a whole-number multiple of the empirical formula.

  5. Determining Chemical Formulas Using Percent Composition:

    • Percent composition = (mass of element in 1 mole of compound / molar mass of compound) × 100.

    • Use percent composition to infer empirical formula.

  6. Calculating Mass Percent Composition of Atoms in a Compound:

    • Mass percent of element = (mass of element in 1 mole of compound / molar mass of compound) × 100.

  7. Drawing Lewis Structures:

    • Follow the octet rule (atoms tend to form bonds until they are surrounded by eight valence electrons).

    • Identify exceptions: e.g., hydrogen (2 electrons), boron (6 electrons), and elements with expanded octets (e.g., P, S).

  8. Applying Electronegativity Trends:

    • Classify bonds:

      • Nonpolar Covalent: Similar electronegativity (difference < 0.4).

      • Polar Covalent: Moderate difference in electronegativity (0.4 - 1.7).

      • Ionic: Large difference in electronegativity (≥ 1.7).

  9. Calculating Formal Charge in Lewis Structures:

    • Formal charge = (valence electrons) - (nonbonding electrons) - 1/2(bonding electrons).

  10. Characteristics of Resonance Structures:

    • Occur when more than one valid Lewis structure can represent a molecule.

    • The actual structure is a resonance hybrid, exhibiting characteristics of all forms.