Naming Ions and Ionic Compounds

Introduction

• Understanding the naming of ions and ionic compounds is crucial in chemistry.
• Focus on naming positive ions (cations), negative ions (anions), and compounds involving main group elements.

Cations and Anions

• Cations: Positively charged ions formed when an atom loses electrons. Example: Sodium (Na) loses one electron to become Na⁺.
• Anions: Negatively charged ions formed when an atom gains electrons. Example: Chlorine (Cl) gains one electron to become Cl⁻.

Main Group Ions

• Elements in groups 1, 2, and 13-18 form ions with predictable charges based on their group.
• Hydrogen is unique as it forms both cations and anions.

Naming Cations

• Add "ion" to the element name for main group cations.
  • Group 1 (1+ charge): Hydrogen (H⁺), Sodium (Na⁺), Potassium (K⁺)
  • Group 2 (2+ charge): Magnesium (Mg²⁺), Calcium (Ca²⁺)
• Polyvalent Cations: Transition metals can have multiple charges.
  • Use Roman numerals to indicate charge: Iron(II) for Fe²⁺, Iron(III) for Fe³⁺.
  • Common names with -ous (lower) and -ic (higher) suffixes are sometimes used.

Naming Anions

• Root of element's name + "-ide"
  • Oxygen (O²⁻) becomes Oxide
  • Chlorine (Cl⁻) becomes Chloride

Formulas of Ionic Compounds

• Combine cations and anions such that the compound is electrically neutral.
• Example: Potassium (K⁺) and Chloride (Cl⁻) form KCl.
• Use lowest possible integer ratio in formulas.
• Example: Mg³P² is Magnesium Phosphide, not Mg₂P₃.

Naming Compounds with Polyvalent Cations

• Specify cation charge with Roman numerals: Lead(IV) Chloride for PbCl₄.
• Some transition metals only form one cation and do not need Roman numerals: Silver (Ag⁺), Zinc (Zn²⁺).

Practice Problems

1. Name: SrF₂ is Strontium Fluoride.
2. Formula: Calcium Bromide is CaBr₂.

Conclusion

• Understanding the charges and naming conventions helps predict and name ionic compounds effectively.
• Charges are often implied and do not need to be stated for main group elements.