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• Forces of Attraction:

  • Attractive forces between molecules allow them to form condensed phases of matter
  • Two primary types of attractive forces:
  • Intramolecular forces hold atoms together within a molecule (chemical bonds)
  • Intermolecular forces exist between molecules
• Intramolecular Forces of Attraction:

  • Three types of chemical bonds:
  • Ionic Bond
  • Covalent Bond
  • Metallic Bond
• Ionic bond:

  • Formed by complete transfer of valence electrons between atoms, producing cations and anions
  • Cations and anions are attracted to each other by Coulombic forces
• Covalent bond:

  • Formed between atoms with similar electronegativities
  • Atoms share electrons to achieve octet configuration and stability
  • Two types of covalent bonds based on electronegativity difference:
  • Nonpolar covalent bond
  • Polar covalent bond
• Nonpolar covalent bond:

  • Formed between same atoms or atoms with very similar electronegativities
  • Electronegativity difference between bonded atoms is less than 0.4
• Polar covalent bond:

  • Formed when atoms of slightly different electronegativities share electrons
  • Electronegativity difference between bonded atoms is between 0.4 and 1.8
• Metallic bond:

  • Occurs between atoms of metals
  • Valence electrons are free to move through the lattice
  • Formed by attraction of mobile electrons (sea of electrons) and fixed positively charged metal ions
• Relative Strength of Intramolecular Forces of Attraction:

  • Metallic bond is the strongest
  • Ionic bond is next
  • Polar covalent bond follows
  • Nonpolar covalent bond is the weakest
• Intermolecular Forces of Attraction:

  • Weaker than intramolecular forces but important for physical properties of molecules
  • Three types:
  • Dipole-dipole interactions
  • Hydrogen bonding
  • Van der Waals forces / London dispersion forces
• Dipole-dipole interactions:

  • Partially positively charged part of one molecule interacts with partially negatively charged part of another
• Hydrogen bonding:

  • Special dipole-dipole interaction between hydrogen atom bonded to oxygen, nitrogen, or fluorine
• London Dispersion (Van der Waals):

  • Arises from temporary dipoles induced in atoms or molecules due to collisions
• Relative strength of intermolecular forces of attraction:

  • Hydrogen bonding is the strongest
  • Dipole-dipole attraction is strong
  • London dispersion attraction is the weakest
• Polarity:

  • Polar covalent bond: Bonding electrons shared unequally
  • Nonpolar covalent bond: Bonding electrons shared equally
  • Electronegativity determines bond polarity
• Acids and Bases:

  • Characteristics of Acids and Bases
  • Definitions of Acids and Bases
  • Arrhenius, Bronsted-Lowry, and Lewis Definitions
• pH Scale:

  • pH measures acidity
  • Neutral solution: pH = 7
  • Acidic solution: pH < 7
  • Basic solution: pH > 7