Overview
This lecture focuses on memorizing common polyatomic ions, their names, formulas, charges, and naming patterns, which are essential for chemical nomenclature and problem-solving in chemistry.
Polyatomic Ion Naming Patterns
- Polyatomic ions are ions containing more than one atom.
- Ions ending in “-ate” have one more oxygen than those ending in “-ite.”
- Monoatomic ions typically end in “-ide” and contain only one atom, usually without oxygen.
- Prefix “per-” indicates one more oxygen than “-ate,” while “hypo-” indicates one less oxygen than “-ite.”
- Adding hydrogen to an ion changes its name to “hydrogen-” or “dihydrogen-” and increases its charge by +1 per hydrogen.
Common Polyatomic Ions: Examples & Names
- NO₃⁻: Nitrate; NO₂⁻: Nitrite; N³⁻: Nitride.
- SO₄²⁻: Sulfate; SO₃²⁻: Sulfite; S²⁻: Sulfide.
- PO₄³⁻: Phosphate; PO₃³⁻: Phosphite; P³⁻: Phosphide.
- ClO₄⁻: Perchlorate; ClO₃⁻: Chlorate; ClO₂⁻: Chlorite; ClO⁻: Hypochlorite; Cl⁻: Chloride.
- Similar patterns apply to bromine (Br) and iodine (I) ions.
Special Cases & Additional Ions
- CO₃²⁻: Carbonate; HCO₃⁻: Hydrogen (bi)carbonate.
- HSO₄⁻: Hydrogen (bi)sulfate; HSO₃⁻: Hydrogen (bi)sulfite.
- H₂PO₄⁻: Dihydrogen phosphate; HPO₄²⁻: Hydrogen phosphate.
- OH⁻: Hydroxide; NH₄⁺: Ammonium; NH₃: Ammonia (neutral molecule).
- C₂H₃O₂⁻: Acetate; C₂O₄²⁻: Oxalate.
- CrO₄²⁻: Chromate; Cr₂O₇²⁻: Dichromate.
- MnO₄⁻: Permanganate.
- S₂²⁻: Disulfide; S₂O₃²⁻: Thiosulfate.
- CN⁻: Cyanide; SCN⁻: Thiocyanate.
- O₂²⁻: Peroxide; O₂⁻: Superoxide.
- N₃⁻: Azide; BO₃³⁻: Borate; H₃O⁺: Hydronium; P₂O₇⁴⁻: Pyrophosphate.
Naming & Formula Practice
- Use patterns for naming: “per-”, “-ate”, “-ite”, “hypo-”, and “-ide.”
- Combine hydrogen addition and charge calculations when naming hydrogen-containing ions.
- Memorize common polyatomic ions and practice writing their formulas and charges.
Key Terms & Definitions
- Polyatomic ion — Ion containing more than one type of atom.
- Monoatomic ion — Ion made of a single atom.
- Suffix “-ate” — Indicates more oxygen atoms.
- Suffix “-ite” — Indicates one less oxygen.
- Suffix “-ide” — Usually for monoatomic ions with no oxygen.
- Prefix “per-” — One more oxygen than “-ate.”
- Prefix “hypo-” — One less oxygen than “-ite.”
- Hydrogen (bi)- — Indicates addition of H⁺, raising the charge by +1 per hydrogen.
- Quiz practice — Naming and writing formulas for given ions.
Action Items / Next Steps
- Memorize the names, formulas, and charges of common polyatomic ions listed above.
- Practice naming ions from formulas and writing formulas from names.
- Review homework or textbook sections on polyatomic ions as assigned by your instructor.