Chapter 3 Molecules and Compounds Libre

Chapter 3 - Molecules and Compounds

• Professor McMahon: General Chemistry I

Key Discovery in Chemistry

• Penicillin: First antibiotic discovered; shared 1945 Nobel Prize by Howard Florey and Ernest Chain for isolating it and determining its chemical formula.

• Ongoing importance of discovering and isolating compounds.

Representation of Chemical Compounds

• Molecular vs. Empirical Formulas:

  • Empirical Formula: Simplest whole-number ratio of elements in a compound (e.g., CH).

  • Molecular Formula: Precise number of each type of atom in a compound.

• Structural Formulas: Illustrates connectivity of atoms in a molecule.

Molecular Elements

• Diatomic Molecules: Elements that exist as two atoms bonded together (e.g., H₂, N₂, O₂).

• Note: Coefficients vs. Subscripts, e.g., H₂ (2 atoms) vs. 2H (2 molecules).

Types of Formulas

• Examples of formulas: Molecular (C₂H₆, CO₂), Empirical (CH), Structural (displays atom connectivity).

Conceptual Application

• Molecular example: Glucose (C₆H₁₂O₆) can determine its molecular and empirical formula.

Isomers

• Definition: Compounds with identical molecular formulas but different structures.

• Types: Structural Isomers (different atoms bonded) and Spatial Isomers (same connectivity but different spatial arrangements).

Ionic and Molecular Compounds

• Ionic Compounds: Form from metal and nonmetal; predictable formulas based on periodic table.

• Molecular Compounds: Form from nonmetals; involves sharing of electrons.

Ions and Charges

• Ions: Charged atoms—Cations (positive) and Anions (negative).

• Ionic charge determined from periodic table positions, aiming for electron count of nearest noble gas.

Polyatomic Ions

• Definition: Group of nonmetals bonded together acting as a single unit (e.g., SO₄²⁻).

Chemical Bonds

• Ionic Bonds: Formed by electron transfer; molecular bonds formed by electron sharing.

• Characteristics of ionic compounds include high melting points and conductivity in solution.

Mole Concept

• Mole: Standard measurement of quantity in chemistry, containing Avogadro’s number (6.022 x 10²³).

• Molar mass: Mass of one mole of a substance in grams.

Percent Composition and Molar Mass

• Percent Composition: Calculation indicating the mass percentage of each element in a compound.

• Example: Iron in Fe₂O₃.

Empirical and Molecular Formulas

• Determining Empirical Formulas: Using mols derived from elemental masses.

• Determining Molecular Formulas: Using the empirical formula and molar mass to find a multiple needed for molecular structure.

Naming Compounds

• Nomenclature: Systematic naming following IUPAC rules for ionic and molecular compounds, including binary acids.

• Recognize between ionic compounds (single/variable charged metals) and molecular compounds.