Objectives

  • Understand the concept of chemical bonding
  • Understand why chemical bonds are formed
  • Familiarize with different types of chemical bonds
  • Revise the concept of electronegativity and its trends in the periodic table

Success Criteria

  • Classify provided compounds according to their bond type
  • Understand the different types of chemical bonds, their stability, and instability factors
  • Understand bond energy and its usage to predict molecule stability
  • Discuss the stability of chemical bonds, compounds, and molecules

Key Concepts of Chemical Bonds

Energy Exchange in Chemical Bonds

  • Bonds involve energy exchange:
    • Energy is released when forming bonds.
    • Energy is absorbed when breaking bonds.
  • Strong bonds result in a greater release of energy during formation and require more energy to break.

Stability of Bonds

  • Stronger bonds correspond to greater stability.
  • Bonds with shorter atomic distances are stronger:
    • Shorter bond lengths imply atoms are closer together, making bonds stronger.
  • Weaker bonds are observed between atoms that are further apart.

Types of Chemical Bonds

Ionic Bonds

  • Occur between metals and nonmetals:
    • One atom loses electrons, resulting in a positive oxidation state.
    • Another atom gains electrons, resulting in a negative oxidation state.
  • Example: Sodium (Na) and Chlorine (Cl) in NaCl.

Covalent Bonds

  • Formed by the sharing of electrons between nonmetals.
  • Types of covalent bonds based on electron sharing:
    • Single bond: sharing of one pair of electrons (e.g., H–H)
    • Double bond: sharing of two pairs of electrons (e.g., O=O)
    • Triple bond: sharing of three pairs of electrons (e.g., N≡N)

Hydrogen Bonds

  • A specific type of attraction that occurs when the positive end of one polar molecule is attracted to the negative end of another polar molecule.
  • Commonly occurs in molecules such as water (H₂O), ammonia (NH₃), and alcohols (OH).
  • Characterized by a significant difference in electronegativity, making these molecules highly polar and reactive.
  • Influences molecular structure and shape.
  • Bond angle in water is approximately 104.5 degrees due to hydrogen bonding.