Overview
This lecture covers the naming conventions for compounds with polyatomic ions and acids, highlighting key rules and memorization requirements for chemical nomenclature.
Polyatomic Ions
- Polyatomic ions are groups of covalently bonded nonmetals with an overall ionic charge.
- Memorize the name, formula, and charge of selected polyatomic ions listed in Table 2.3 for this course.
- Important polyatomic ions: acetate, carbonate, bicarbonate, cyanide, hypochlorite, chlorite, chlorate, perchlorate, ammonium, nitrite, nitrate, hydroxide, phosphite, phosphate, sulfite, sulfate.
- Ammonium (NH₄⁺) is the only required polyatomic ion with a positive charge.
- Using tools like flashcards or Quizlet helps in memorizing polyatomic ions.
Naming Compounds with Polyatomic Ions
- All compounds with polyatomic ions are considered ionic compounds.
- Apply standard ionic naming rules and use polyatomic ion names directly.
- Example: NH₄Cl → ammonium chloride; Ba(OH)₂ → barium hydroxide.
- For compounds with metal cations that have variable charges (e.g., lead), indicate the charge using Roman numerals.
- To write chemical formulas from names, use ion charges to balance and apply the crisscross method for subscripts.
- Example: Iron(III) chlorate → Fe(ClO₃)₃; Ammonium sulfide → (NH₄)₂S.
Naming Acids
- Acids donate H⁺ ions and typically have formulas starting with H.
- The name of an acid depends on the suffix of its anion:
- Anions ending in "-ide": hydro___ic acid (e.g., H₂S → hydrosulfuric acid).
- Anions ending in "-ite": ___ous acid.
- Anions ending in "-ate": ___ic acid (e.g., HClO₄ → perchloric acid).
- Molecular names of acids convert based on the above rules.
Key Terms & Definitions
- Polyatomic ion — a group of covalently bonded atoms with an overall ionic charge.
- Ionic compound — a compound composed of positive and negative ions.
- Acid — a substance that donates H⁺ ions and begins with H in its formula.
- Crisscross method — technique to balance ionic charges in formulas.
- Suffixes for acid naming — rules for naming acids based on their anion ending (-ide, -ite, -ate).
Action Items / Next Steps
- Memorize names, formulas, and charges of required polyatomic ions.
- Practice naming and writing formulas for compounds with polyatomic ions and acids.
- Review acid naming rules; prepare for more details in Chapter 4.