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CHEM 111 Unit 8

Periodic Table Overview

  • Key elements listed with atomic numbers and masses:

    • 1 (Hydrogen): 1.008

    • 3 (Lithium): 6.94

    • 11 (Sodium): 22.99

    • 12 (Magnesium): 24.31

    • 19 (Potassium): 39.10

Types of Chemical Bonds

  • Ionic Bonds: Electrons transferred; metal to nonmetal.

  • Covalent Bonds: Electrons shared; nonmetal to nonmetal.

  • Metallic Bonds: Electrons pooled; metal to metal.

Bonding Theories

  • Lewis Theory: Atoms lose, gain, or share electrons to achieve Noble Gas configuration.

    • Valence Electrons: Involved in bonding, represented using Lewis structures.

Ionic Bonds Characteristics

  • Cations: Formed by metals losing electrons.

  • Anions: Formed by non-metals gaining electrons.

  • Ions' size: Cations smaller than original atom; anions larger.

Lattice Energy

  • Higher energy associated with larger ion charges (Q) and smaller distances (r).

  • Mathematical expression: E = k \frac{Q^+ Q^-}{r}.

Covalent Bonds

  • Bonding Pairs: Shared electrons; Lone Pairs: Unshared electrons.

  • Bond Length: Based on atomic sizes.

  • Bond Order: Indicates strength; higher order = stronger bond.

Formal Charge Calculation

  • Formula: FC = VE - (bonds) - (lone pair electrons).

Molecular Geometry

  • Determined by electron pair arrangements (VSEPR Model):

    • 2 pairs: Linear

    • 3 pairs: Trigonal Planar

    • 4 pairs: Tetrahedral

    • 5 pairs: Trigonal Bipyramidal

    • 6 pairs: Octahedral.

Electronegativity and Bond Polarity

  • Electronegativity increases across a period and decreases down a group.

  • Polar bond: High difference in electronegativity. Nonpolar bond: Similar electronegativities.

Learning Objectives for Unit 8

  • Understand ionic bond formation and lattice energy.

  • Write electron configurations, Lewis structures, and resonance structures.

  • Relate bond order to length and predict geometries from Lewis structures.