Chemical Bonding: Ionic and Covalent Compounds

Part 1: Classifying Compounds

• Ionic Compounds:

  • Form between metals (+) and nonmetals (–).
  • Electrons are transferred, creating ions.
  • Examples: NaCl, CaCl₂.

• Covalent (Molecular) Compounds:

  • Form between nonmetals only.
  • Electrons are shared.
  • Examples: H₂O, CO₂.

Part 2: Writing Formulas

• Ionic Compounds:

  • Naming: Metal first, then nonmetal with "-ide" (e.g., NaCl = sodium chloride).
  • Polyatomic ions remain grouped (e.g., K₂CO₃ = potassium carbonate).

• Covalent Compounds:

  • Use prefixes (mono-, di-, tri-) to indicate atom counts (e.g., NCl₃ = nitrogen trichloride).

Part 3: Drawing Structures

• Lewis Structures (Covalent Bonds):

  • Show shared electron pairs as lines, lone pairs as dots.
  • Example: CO₂ structure is linear, no lone pairs on carbon.

• Ionic Structures:

  • No sharing, ions form a lattice (e.g., CaF₂).

• Diatomic Molecules:

  • Exist as two-atom molecules: H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂.

• Organic Molecule: -organic molecules all have carbon -a hydrocarrbon is an organic compound containing Hydrogen and Carbon

-first place a Carbon at the ENDS & BENDS of a skeleton structure -then, fill in with Hydrogen atoms until every carbon has 4 BONDS

Part 4: Electronegativity and Polarity

• Polar vs. Nonpolar Bonds:

  • Polar covalent: Unequal electron sharing (e.g., H₂O).
  • Nonpolar covalent: Equal electron sharing (e.g., O₂).

• Determining Polarity:

  • Electronegativity difference:

    • 1.7 = Ionic.

    • 0.5–1.7 = Polar covalent.
    • <0.5 = Nonpolar covalent.
  • Molecular shape influences polarity (e.g., CO₂ is nonpolar despite polar bonds).

Part 5: Water is Amazing!

• Why Water is Polar:

  • Oxygen pulls electrons from hydrogen, creating partial charges (δ⁺ on H, δ⁻ on O).

• Hydrogen Bonding:

  • Attraction between δ⁺ H of one molecule and δ⁻ O of another.
  • Results in unique properties: high boiling point, surface tension, capillary action.

• Capillary action: -water ability to climb UP skinny tubes, using cohesion & adhesion -water is able to stick to the walls of a skinny tube, which allows other water molecules to stick to that water molecule, creating a chain of water molecules

-High Heat Capacity: -water is really good at holding onto heat

-Super Solvent: -water is good at dissolving many substances

Part 6: Comparing Ionic and Covalent Compounds

• Ionic Properties:
  • High melting point due to the big. charges that keep ions strongly attracted to eachother. -conductive when dissolved due to high amount of loose ions when dissolved. -will dissolve and dissociate in water because charges attract H2O which pulls ions apart. The negative oxygen will be attracted to the positive end of the ionic compound while the positive hydrogen will go after the negative part of the

-Polar Covalent Properties: -medium melting point because partial charges create attraction between atoms -not conductive -dissolves BUT DOESNT DISSOCIATE, partial charges attract H2O which surrounds molecule

• **NonPolar Covalent Properties **:

• Low melting point due to no charges to hold molecules together. -nonconductive. nonpolar compounds are insoluble in water.

• Example Clues:

  • White crystal that conducts when dissolved is likely ionic.
  • Gas at room temperature is likely nonpolar covalent because no charges for water to stick to.

Part 7: Molarity Math

• Molarity (M) Formula:

  • M = moles of solute / liters of solution.
  • Example: 4.5 moles of NaCl in 3 L solution = 1.5 M.

• Conductivity:

  • More ions result in better conductivity (e.g., NaCl vs. sugar).

Part 8: Science Sketches

• Nonpolar Substance Melting:

  • Weak London dispersion forces break easily when heated.

• Ionic Dissociation in Water:

  • Water molecules surround ions.
  • Oxygen (δ⁻) faces positive ions (Na⁺), Hydrogen (δ⁺) faces negative ions (Cl⁻).

Summary

• Ionic Bonds: Metal + nonmetal, electrons transferred.
• Covalent Bonds: Nonmetals only, electrons shared.
• Polarity: Depends on electronegativity and molecular shape.
• Water's Properties: Due to hydrogen bonding.
• Molarity: Measures solution concentration.