Lecture Notes: Chemical Bonds, Ionic Compounds, and Naming Conventions

Introduction

• Presentation covers sections 2.6 and 2.7 combined.
• Focus on chemical bonds, specifically ionic and covalent bonds.

Chemical Bonds

• Atoms and Electrons: Atoms gain/lose electrons to form bonds.
• Molecules: Groups of atoms bonded with no net charge, either through covalent or ionic bonds.

Ionic Bonds

• Definition: Form through attraction between positive (cation) and negative (anion) ions.
  • Stronger than covalent bonds
• Example: Sodium (Na) loses an electron to Chlorine (Cl), forming NaCl (sodium chloride).
• Characteristics:
  • High melting points
  • Dissolve in water
  • Typically solids at room temperature
• Formation: Crisscross method for writing ionic compound formulas:
  • Charge on cation becomes subscript on anion and vice versa.
  • Simplify formulas to empirical form.

Formulas and Examples

• Lithium Bromide: LiBr (simplified from Li1Br1)
• Barium Chloride: BaCl2
• Calcium Oxide: CaO (simplified from Ca2O2)
• Aluminum Sulfide: Al2S3
• Lithium Sulfate: Li2SO4
• Magnesium Hydroxide: Mg(OH)2
• Iron(III) Sulfate: Fe2(SO4)3

Naming Ionic Compounds

• Monatomic Ions: Add 'ide' suffix to anions.
• Polyatomic Ions: Names generally unchanged unless in acids.
• Transition Metals: Use Roman numerals to denote charge.

Rules for Oxidation Numbers

• Elemental Form: Oxidation number is zero.
• Oxygen: Typically -2.
• Hydrogen: Typically +1.
• Sum in neutral compounds equals zero.

Naming Rules and Examples

• Binary Molecular Compounds: Use Greek prefixes (mono, di, tri, etc.)
• Examples:
  • CO: Carbon monoxide
  • SO2: Sulfur dioxide
  • P2S3: Diphosphorus trisulfide
  • N2O: Dinitrogen oxide (also known as nitrous oxide or laughing gas)
  • NH3: Nitrogen trihydride (commonly known as ammonia)

Acids

• Hydrogen Ions: Acids donate hydrogen ions to water.
• Naming:
  • No oxygen: Prefix 'hydro-', suffix '-ic' (e.g., HCl: hydrochloric acid)
  • With oxygen: 'ate' becomes '-ic', 'ite' becomes '-ous' (e.g., H2SO4: sulfuric acid)

Bases

• Contain hydroxide ions, named following polyatomic ion rules (e.g., NaOH: sodium hydroxide).

Examples of Naming and Writing Formulas

• Ionic Compounds: Name using metal + non-metal 'ide' (e.g., MgCl2: magnesium chloride)
• Covalent Compounds: Use prefixes for non-metals (e.g., NCl3: nitrogen trichloride)
• Acid Naming: Based on presence of oxygen and other rules.

Practice Problems

• Practice naming compounds, writing formulas, and understanding ions using periodic table references.
• Familiarity with polyatomic ions important for naming and predicting compound behavior.