Lecture on Chemical Nomenclature

Introduction

• Nomenclature Definition: The act or process of naming.
• Focus: Naming chemical compounds and writing their formulas.
• Importance: Strong foundation in nomenclature is crucial for understanding chemical reactions.

Goals of the Unit

• Name ionic compounds (main group, transition metals), covalent compounds, acids, and bases using IUPAC rules.
• Write formulas for these compounds.
• Mastery involves writing names from formulas and vice versa.

IUPAC

• International Union of Pure and Applied Chemistry.
• Governs naming and formula rules in chemistry.

Chemical Formulas

• Molecular Formula: Shows type and number of each element.
• Empirical Formula: Shows elements in the lowest whole number ratio.
• Subscripts: Indicate the number of atoms (e.g., H₂O).

Ionic Nomenclature

• Cations: Metals losing electrons, gaining positive charge.
• Anions: Nonmetals gaining electrons, gaining negative charge.
• Polyatomic Ions: Groups of bonded elements with an overall charge (e.g., ammonium NH₄⁺, nitrate NO₃⁻).
• Ionic compounds can be nonmetal-cation combinations (e.g., NH₄NO₃).

Transition Metals

• Can form multiple cations due to d orbital valence electrons.
• Specific oxidation numbers needed; provided in problems.

Writing Chemical Formulas

1. Write symbol and oxidation number (positive ion first).
2. Crisscross numbers, write as subscripts (without signs).
   • If multiples, reduce them.
3. Use parentheses for polyatomic ions when needed.

Naming Ionic Compounds

• Name the metal, change nonmetal ending to "ide".
• Name polyatomic ions as is.
• Transition metals need oxidation numbers in Roman numerals.

Exceptions

• Group 1, 2, and Aluminum, Zinc, Cadmium (always specific charges) don't need Roman numerals.

Practice Examples

• Naming and writing formulas for various combinations of elements and compounds, including using and understanding polyatomic ions and transition metal oxidation numbers.

Conclusion

• Mastery of chemical nomenclature is foundational for progressing in chemistry.
• More complex naming systems (like covalent) to follow in future lectures.