Summary of Electronegativity and Bonding

Electronegativity

  • Definition: Ability of an atom to attract electrons in a covalent bond.
  • Pauling Scale: Fluorine (4.0) is the most electronegative atom.

Factors Influencing Electronegativity

  1. Nuclear Charge:

    • More protons = stronger attraction for electrons = increased electronegativity.

  2. Atomic Radius:

    • Larger radius = weaker attraction to the nucleus = decreased electronegativity.

  3. Shielding:

    • Inner electron shells reduce nuclear charge effect on outer electrons = decreased electronegativity.

Trends in Electronegativity

  • Down a Group:

    • Electronegativity decreases due to increased atomic radius and shielding despite increased nuclear charge.

  • Across a Period:

    • Electronegativity increases due to increased nuclear charge and constant shielding, resulting in smaller atomic radii.

Predicting Bond Formation

  • Covalent Bonds:

    • Formed by equal sharing of electrons between atoms with similar electronegativities.
    • Nonpolar (equal sharing) vs. Polar (unequal sharing).

  • Ionic Bonds:

    • Large difference in electronegativities = electron transfer from less electronegative to more electronegative atom, creating cations (positive) and anions (negative).

Exam Tips

  • Trends: Electronegativity increases to top right of Periodic Table (Fluorine = most electronegative).
  • Use Pauling scale for determining bond type based on electronegativity differences:
    • < 1.0: Covalent
    • 1.0 - 2.0: Polar Covalent
    • > 2.0: Ionic