Covalent and Ionic Bonds

Covalent Bonds

• Definition: Involves the sharing of electrons between atoms.
• Example: Two hydrogen atoms form a covalent bond by sharing electrons.

Ionic Bonds

• Definition: Formed through the transfer of electrons from one atom to another, resulting in electrostatic attraction between oppositely charged ions.
• Example: Sodium and chlorine form an ionic bond; sodium becomes a cation (+) and chlorine becomes an anion (-).

Differences Between Covalent and Ionic Bonds

• Covalent Bonds:
  • Electrons are shared.
  • Typically between nonmetals.
• Ionic Bonds:
  • Electrons are transferred.
  • Typically between metals and nonmetals.
  • Characterized by electrostatic forces.

Polar vs Nonpolar Covalent Bonds

Nonpolar Covalent Bonds

• Characteristics:
  • Electrons are shared equally between atoms.
  • Occurs when atoms have the same electronegativity.
  • Example: H-H bond in hydrogen gas.

Polar Covalent Bonds

• Characteristics:
  • Electrons are shared unequally due to different electronegativities.
  • Results in partial positive and negative charges, creating a dipole.
  • Example: H-F bond in hydrogen fluoride; fluorine pulls electrons more strongly.

Electronegativity and Bond Type

• Nonpolar Covalent: Electronegativity difference of 0 to 0.4.
• Polar Covalent: Electronegativity difference of 0.5 to 1.9.
• Ionic: Electronegativity difference greater than 1.9.

Identifying Bond Types

• Ionic Bonds:
  • Formed by ions with opposite charges.
  • Typically between metals and nonmetals.
• Polar vs Nonpolar Covalent:
  • Use electronegativity values.
  • If difference is 0.5 or more, bond is polar.

Example Problems

Identifying Bonds

• Chlorine Molecule (Cl-Cl):

  • Two nonmetals, same element -> Nonpolar covalent bond

• Carbon-Hydrogen Bond (C-H):

  • Both nonmetals, different elements
  • Electronegativity difference: 0.4 -> Nonpolar covalent bond

• Carbon-Oxygen Bond (C-O):

  • Both nonmetals
  • Electronegativity difference: 1.0 -> Polar covalent bond

• Sodium-Fluoride Bond (Na-F):

  • Metal and nonmetal
  • Electronegativity difference: 3.1 -> Ionic bond

Determining Most Polar Bond

• Example 1: Nitrogen-Fluorine, Phosphorus-Fluorine, Arsenic-Fluorine

  • Arsenic is furthest from fluorine on the periodic table -> Arsenic-Fluorine is most polar

• Example 2: Carbon-Fluorine, Nitrogen-Fluorine, Oxygen-Fluorine

  • Carbon is furthest from fluorine -> Carbon-Fluorine is most polar

Key Concepts

• Electronegativity: Measure of an atom's ability to attract shared electrons.
• Periodic Table Trends: Distance between elements affects the polarity of bonds without needing electronegativity values.