ch04

Chapter Overview

• Nomenclature is the systematic approach to naming chemical compounds.

• Chemical formulas are used to represent compounds combining symbols and subscripts.

Section 4.1: Chemical Formulas

• Interpretation of Chemical Formulas:

  • Chemical formulas indicate the ratio of elements in a compound.

  • Example:

    • Fe2O3: rust

    • O2: elemental oxygen

• Components of Chemical Formulas:

  • Symbols identify elements (e.g., H, C, O).

  • Subscripts indicate the number of atoms of each element.

  • Parentheses are used for groups of atoms (e.g., Ba3(PO4)2 represents Ba, P, and O).

• Example of Formula Unit:

  • Ba3(PO4)2 contains:

    • 3 Ba atoms

    • 2 P atoms

    • 8 O atoms

Section 4.2: Naming Binary Covalent Compounds

• Binary Covalent Compounds: Composed of two nonmetals.

• Use of Prefixes:

  • 1 = mono-, 2 = di-, 3 = tri-, 4 = tetra-, etc.

• Naming Rules:

  • Name the first element, add a prefix if more than one atom is present.

  • Modify the second element's name to end in -ide (e.g., N2O is dinitrogen monoxide).

• Examples:

  • Silicon tetrachloride: SiCl4

  • Sulfur trioxide: SO3

Section 4.3: Formulas for Ionic Compounds

• Ionic Compounds: Formed between metals and nonmetals; consist of cations and anions.

• Identifying Ionic Formulas:

  • Compounds must be electrically neutral (total positive charge = total negative charge).

  • Example: AlCl3 is formed from Al3+ and Cl− ions.

• Polyatomic Ions: Groups of atoms with a net charge. Examples include:

  • Ammonium (NH4+), Carbonate (CO32-).

Section 4.4: Naming Ionic Compounds

• Naming Convention: Name the cation first followed by the anion.

• Types of Cations:

  • Polyatomic, monatomic (constant or variable charge).

• Variable Charge Examples:

  • Fe2+: iron(II) ion

  • Fe3+: iron(III) ion

• Naming Polyatomic Ions: Must be memorized or referred to in a table.

Section 4.5: Naming Acids

• Acids: Release H+ ions when dissolved in water.

• Types of Acids:

  • Binary Acids: Follow the pattern hydro- + root of anion + -ic (e.g., HCl = hydrochloric acid).

  • Oxyacids: Derived from oxyanions, follow naming rules.

  • For -ate ions, use -ic acid; for -ite ions, use -ous acid.

• Examples:

  • Phosphoric acid (H3PO4) and Chloric acid (HClO3).

Section 4.6: Nomenclature Review

• Summary of Naming Systems:

  • Determine whether a compound is ionic or covalent.

  • Identify the type of ions and where applicable use prefixes for covalent compounds.

  • For hydrates, add a prefix + hydrate to the name.

• Naming Examples:

  • NaCl -> sodium chloride

  • CuS -> copper(I) sulfide

Important Terms and Examples

• Diatomic Molecules: H2, N2, O2, F2, Cl2, Br2, I2.

• Allotropes of Carbon: Diamond, Graphite, Fullerenes, Nanotubes.

• Common Polyatomic Ions Examples:

  • Nitrate (NO3-), Sulfate (SO42-), Phosphate (PO43-).

• Binary Compounds of Hydrogen: NH3 (ammonia), PH3 (phosphine).

Section Reviews Summary

• Review the key points of previous sections before moving to more complex naming conventions and structures.