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Polyatomic Ions and Elements Overview

Aug 12, 2025

Overview

This lecture provides a list of key polyatomic ions (PAI) and chemical elements encountered in AP Chemistry, including their names, symbols, and some examples.

Common Polyatomic Ions (PAIs)

  • Carbonate ion is represented by the formula CO₃²⁻.
  • Nitrite ion is represented by the formula NO₂⁻.
  • Nitrate ion is represented by the formula NO₃⁻.
  • Sulfate ion is represented by the formula SO₄²⁻.
  • Sulfite ion is represented by the formula SO₃²⁻.
  • Phosphate ion is represented by the formula PO₄³⁻.
  • Ammonium ion is represented by the formula NH₄⁺.
  • Hydroxide ion is represented by the formula OH⁻.
  • Acetate ion is represented by the formula C₂H₃O₂⁻ or CH₃COO⁻.
  • Cyanide ion is represented by the formula CN⁻.
  • Permanganate ion is represented by the formula MnO₄⁻.
  • Chromate ion is represented by the formula CrO₄²⁻.
  • Dichromate ion is represented by the formula Cr₂O₇²⁻.

Common Chemical Elements

  • Hydrogen has the symbol H.
  • Carbon has the symbol C.
  • Nitrogen has the symbol N.
  • Oxygen has the symbol O.
  • Sulfur has the symbol S.
  • Phosphorus has the symbol P.
  • Chlorine has the symbol Cl.
  • Sodium has the symbol Na.
  • Potassium has the symbol K.
  • Calcium has the symbol Ca.
  • Magnesium has the symbol Mg.
  • Iron has the symbol Fe.
  • Copper has the symbol Cu.
  • Silver has the symbol Ag.
  • Zinc has the symbol Zn.

Key Terms & Definitions

  • Polyatomic ion (PAI) — Ion composed of two or more atoms bonded covalently with a net charge.
  • Ion — Atom or group of atoms that has gained or lost electrons, resulting in a net charge.
  • Element — Pure substance consisting of only one type of atom.

Action Items / Next Steps

  • Memorize the names, symbols, and formulas of common polyatomic ions and elements for AP Chemistry quizzes and exams.
  • Practice writing and identifying these ions and elements in chemical compounds.