Overview
This lecture explains how to determine the charge of chemical ions, including how to use the periodic table, important molecular ions to memorize, and note-taking strategies.
Note-Taking Setup
- Write your name, the title ("Charges" or "How to Find a Charge"), and the date at the top of your notes.
- Draw a left column for questions and a large right area for notes, leaving space at the bottom for a summary.
Introduction to Ions
- An atom with a charge is called an ion.
- Ions can have positive or negative charges.
- Do not refer to charged particles as atoms in exams; always use "ion."
Charges of Metal Ions
- Metals are on the left side of the periodic table, separated by the boron step.
- Group 1 metals form ions with a 1+ charge.
- Group 2 metals form ions with a 2+ charge.
- Group 3 metals form ions with a 3+ charge (except boron).
- Transition metals (d-block) have variable charges; common ones to memorize:
- Copper (usually 2+, sometimes 1+)
- Zinc (2+)
- Iron (2+ or 3+)
- Silver (1+)
Charges of Nonmetal Ions
- Nonmetals are on the right side of the periodic table.
- Noble gases have no charge (0).
- Halogens (e.g., fluorine, chlorine) have a 1– charge.
- Oxygen group (e.g., oxygen, sulfur) have a 2– charge.
- Nitrogen group (e.g., nitrogen, phosphorus) have a 3– charge.
Molecular (Polyatomic) Ions
- Molecular ions consist of more than one atom and are not found on the periodic table.
- Key molecular ions to memorize:
- Nitrate: NO₃⁻
- Sulfate: SO₄²⁻
- Carbonate: CO₃²⁻
- Hydroxide: OH⁻
- Ammonium: NH₄⁺
- Phosphate: PO₄³⁻
- You must memorize the formulas and charges of molecular ions.
Using and Reviewing Your Notes
- In class, focus on quick, concise notes; add questions and summaries at home.
- Write a question next to each key fact or method to help review later.
- Create a summary at the bottom of your notes to reinforce main ideas.
Key Terms & Definitions
- Ion — An atom or molecule with a net electrical charge.
- Molecular ion (Polyatomic ion) — An ion composed of two or more atoms bonded together.
- d-block (Transition metals) — The central block of the periodic table with elements that often have variable charges.
Action Items / Next Steps
- Memorize the charges for transition metals and key molecular ions.
- After class, add questions and a summary to your notes for better review.
- Practice recalling molecular ions by writing them repeatedly from memory.