Overview
This lecture explains a mnemonic for remembering the formulas and charges of common polyatomic ions using the phrase "Nick the Camel ate a Clam for Supper in Phoenix" and discusses exceptions and hydrogen polyatomics.
Mnemonic for Polyatomic Ions
- The underlined letter in each mnemonic word represents a chemical element (e.g., N = nitrogen, C = carbon, Cl = chlorine, S = sulfur, P = phosphorus).
- The number of consonants in each mnemonic word equals the number of oxygen atoms in the ion.
- The number of vowels in each word equals the negative charge on the ion.
Examples Using the Mnemonic
- "Nick" (N): 3 consonants (NO₃), 1 vowel (-1 charge) → nitrate: NO₃⁻
- "Camel" (C): 3 consonants (CO₃), 2 vowels (-2 charge) → carbonate: CO₃²⁻
- "Clam" (Cl): 3 consonants (ClO₃), 1 vowel (-1 charge) → chlorate: ClO₃⁻
- "Supper" (S): 4 consonants (SO₄), 2 vowels (-2 charge) → sulfate: SO₄²⁻
- "Phoenix" (P): 4 consonants (PO₄), 3 vowels (-3 charge) → phosphate: PO₄³⁻
Polyatomic Ions Not Following the Mnemonic
- Ammonium: NH₄⁺ (positive charge, treated as a metal-like ion)
- Hydroxide: OH⁻
Hydrogen Polyatomics
- Adding hydrogen to carbonate (CO₃²⁻) makes it HCO₃⁻ (charge decreases by one).
- Adding hydrogen to sulfate (SO₄²⁻) makes it HSO₄⁻ (charge decreases by one).
- Adding hydrogen to phosphate (PO₄³⁻) makes it HPO₄²⁻ (charge decreases by one).
- Hydrogen polyatomics do not exist for nitrate or chlorate.
Key Terms & Definitions
- Polyatomic ion — a charged species composed of two or more atoms covalently bonded.
- Mnemonic — a memory aid for recalling specific information.
- Hydrogen polyatomic — a polyatomic ion formed by adding hydrogen, reducing the charge by one.
Action Items / Next Steps
- Memorize the mnemonic and associated ion formulas and charges.
- Learn ammonium and hydroxide ions; memorize hydrogen polyatomics for carbonate, sulfate, and phosphate.
- Practice writing and naming these polyatomic ions.