Chemical Structure and Bonds Quiz

Chemical Structure and Bonds

• A chemical bond is a force that holds atoms together in a molecule or compound.
• Ionic Bonds: Transfer of electrons between a metal (cation) and a nonmetal (anion). Example: NaCl
• Covalent Bonds: Sharing of electrons between two nonmetals.
  • Polar Covalent: Significant electronegativity difference (H₂O).
  • Nonpolar Covalent: Similar electronegativity (O₂).
• Metallic Bonds: Delocalized electrons in a "sea" of electrons. Example: Fe

Properties of Bonds

• Ionic Bonds:
  • High melting and boiling points.
  • Good conductors in liquid or solution state.
  • Soluble in water.
• Covalent Bonds:
  • Nonpolar Covalent: Insoluble in water, soluble in organic solvents.
  • Polar Covalent: Soluble in water.
  • Do not conduct electricity.
• Metallic Bonds:
  • Good conductors of electricity and heat.
  • Malleable and ductile.

Electronegativity and Polarity

• Electronegativity: An atom's ability to attract electrons in a bond.
  • Difference < 0.4 → Nonpolar covalent.
  • 0.4 < Difference < 1.7 → Polar covalent.
  • Difference ≥ 1.7 → Ionic.
• Dipole moment: Measures the polarity of a molecule. Polar molecules have non-zero dipole moments.

Molecular Geometry and VSEPR Theory

• Molecular geometry is determined by Valence Shell Electron Pair Repulsion (VSEPR) theory.
• Common Geometries:
  • Linear: CO₂, BeCl₂ (180° angle)
  • Trigonal planar: BF₃ (120° angle)
  • Tetrahedral: CH₄ (109.5° angle)
  • Trigonal pyramidal: NH₃ (<109.5° angle)
  • Bent: H₂O (<109.5° angle)

Intermolecular Forces

• Hydrogen bonds: Strong attraction between H and F, O, or N.
• Dipole-dipole forces: Attractions between polar molecules.
• London Dispersion Forces: Present in all molecules, especially nonpolar ones.