Overview
This lecture covers the memorization of common polyatomic ions, including their names, formulas, charges, and naming patterns, essential for chemistry problem-solving.
Naming Patterns & Rules
- Polyatomic ions contain multiple atoms; monoatomic ions consist of single atoms.
- Suffix "-ate" means one more oxygen than "-ite."
- Monoatomic ions often end in "-ide" and lack oxygen.
- Prefix "per-" adds one oxygen; "hypo-" removes one oxygen relative to "-ite."
- Adding hydrogen to an ion increases the positive charge by +1 each time.
Common Polyatomic Ions & Examples
- NO₃⁻ — Nitrate; NO₂⁻ — Nitrite; N³⁻ — Nitride (monoatomic).
- SO₄²⁻ — Sulfate; SO₃²⁻ — Sulfite; S²⁻ — Sulfide (monoatomic).
- PO₄³⁻ — Phosphate; PO₃³⁻ — Phosphite; P³⁻ — Phosphide (monoatomic).
- Cl⁻ — Chloride; ClO⁻ — Hypochlorite; ClO₂⁻ — Chlorite; ClO₃⁻ — Chlorate; ClO₄⁻ — Perchlorate.
- Similar patterns apply for bromine (Br) and iodine (I) ions.
- CO₃²⁻ — Carbonate; HCO₃⁻ — Hydrogen carbonate (bicarbonate).
- HSO₄⁻ — Hydrogen sulfate (bisulfate); HSO₃⁻ — Hydrogen sulfite (bisulfite).
- HPO₄²⁻ — Hydrogen phosphate; H₂PO₄⁻ — Dihydrogen phosphate.
- OH⁻ — Hydroxide; NH₄⁺ — Ammonium.
- C₂H₃O₂⁻ — Acetate; C₂O₄²⁻ — Oxalate.
- CrO₄²⁻ — Chromate; Cr₂O₇²⁻ — Dichromate.
- MnO₄⁻ — Permanganate.
- S₂²⁻ — Disulfide; S₂O₃²⁻ — Thiosulfate.
- CN⁻ — Cyanide; SCN⁻ — Thiocyanate.
- O₂²⁻ — Peroxide; O₂⁻ — Superoxide; O²⁻ — Oxide.
- N₃⁻ — Nitride (monoatomic); N₃⁻ (azide) — Polyatomic.
- BO₃³⁻ — Borate; H₃O⁺ — Hydronium.
- P₂O₇⁴⁻ — Pyrophosphate.
Key Terms & Definitions
- Polyatomic ion — An ion containing more than one atom.
- Monoatomic ion — An ion with only one atom.
- Nitrate (NO₃⁻) — Polyatomic ion with one nitrogen and three oxygens, charge -1.
- Nitrite (NO₂⁻) — Polyatomic ion with one nitrogen and two oxygens, charge -1.
- Hydroxide (OH⁻) — Polyatomic ion with oxygen and hydrogen, charge -1.
- Ammonium (NH₄⁺) — Polyatomic ion with nitrogen and four hydrogens, charge +1.
- Acetate (C₂H₃O₂⁻) — Polyatomic ion with two carbons, three hydrogens, two oxygens, charge -1.
- Permanganate (MnO₄⁻) — Polyatomic ion with manganese and four oxygens, charge -1.
- Thiosulfate (S₂O₃²⁻) — Polyatomic ion with two sulfurs, three oxygens, charge -2.
Action Items / Next Steps
- Memorize the names, formulas, and charges for all listed polyatomic ions.
- Practice writing formulas from ion names and vice versa as shown in examples.
- Review the naming rules for "-ate," "-ite," "per-," and "hypo-."
- Prepare for quizzes/tests by recalling ions without reference.