Naming Ionic Compounds
Learning Objectives
- Understand the rules for naming ionic compounds.
- Familiarize with the nomenclature of monatomic and polyatomic ions.
Naming Ions
Cations
- Monatomic Cations: Name of the element followed by "ion".
- Na⁺: Sodium ion
- Al³⁺: Aluminum ion
- Ca²⁺: Calcium ion
- Multiple Charges: Elements like iron can form cations with different charges.
- Stock System: Use Roman numerals to indicate charge.
- Fe²⁺: Iron(II) ion
- Fe³⁺: Iron(III) ion
- Common System: Uses suffixes -ic (higher charge) and -ous (lower charge) with element stems.
- Fe²⁺: Ferrous ion
- Fe³⁺: Ferric ion
Common Cations
| Element | Charge | Modern Name | Common Name |
|---|
| Iron | 2+ | Iron(II) ion | Ferrous ion |
| 3+ | Iron(III) ion | Ferric ion |
| Copper | 1+ | Copper(I) ion | Cuprous ion |
| 2+ | Copper(II) ion | Cupric ion |
Anions
- Monatomic Anions: Stem of element name + "-ide" + "ion".
- Cl⁻: Chloride ion
- O²⁻: Oxide ion
- Common Anions
| Ion | Name |
|--------|--------------|
| F⁻ | Fluoride ion |
| Cl⁻ | Chloride ion |
| O²⁻ | Oxide ion |
Naming Binary Ionic Compounds
- Binary Ionic Compounds: Composed of monatomic metal cation and monatomic nonmetal anion.
- Named as: Name of metal cation + base name of nonmetal anion + suffix -ide.
- Example: BaCl₂ is named as barium chloride.
Examples
- CaCl₂: Calcium chloride
- AlF₃: Aluminum fluoride
- KCl: Potassium chloride
Naming Ionic Compounds with Polyatomic Ions
- Follow the same process as binary ionic compounds.
- Cation named first, anion second.
Examples
- (NH₄)₂S: Ammonium sulfide
- AlPO₄: Aluminum phosphate
- Fe₃(PO₄)₂: Iron(II) phosphate
Summary
- Naming Order: Cation first, anion second.
- Charge Balance: Positive and negative charges must balance.
- Roman Numerals: Used for metals with multiple charge states.
- Ternary Compounds: Composed of three or more elements.
This guide provides a structured approach to understanding the systematic naming of ionic compounds, ensuring clarity in distinguishing between elements with multiple ionic forms and recognizing the crucial balance of charges within compounds.