Ionic Names and Formulas Walkthrough

Key Concepts

• Naming Ionic Compounds: Combine the name of the first element with the name of the second element, changing the ending to "-ide".
• Transition Metals: These elements can have multiple charges, requiring Roman numerals to indicate their charge in compounds.

Detailed Examples

Iron Oxide

• Formula: Fe₂O₃
• Naming: Iron (III) Oxide
• Explanation:
  • Oxygen is in group 16, with a consistent charge of -2.
  • Formula indicates 3 oxygen atoms: Total charge = -6.
  • 2 iron atoms must balance with a charge of +6 total, so each iron has a +3 charge.

Group 1 Metals and Group 16 Nonmetals

• Characteristics:
  • Group 1 metals: +1 charge.
  • Group 16 nonmetals: -2 charge.
• Ratio: 2:1, to balance charges.

Crisscross Method for Formulas

• Example: A (+1) and B (-3)
• Formula: A₃B
• Method: Swap numerical values of charges for subscripts.

Elements Forming Ions

• Negative Ions: Formed by nonmetals.
  • Metals form positive ions.
  • Metalloids and noble gases typically do not form ions.

Ion Charge Changes

• Positive Ion Formation: Lose electrons.
• Negative Ion Formation: Gain electrons.

Practice Examples

Binary Compounds

• Magnesium Sulfide

  • Formula: MgS
  • Explanation: Magnesium (+2) and Sulfur (-2) balance each other out.

• Potassium Nitride

  • Formula: K₃N
  • Explanation: Potassium (+1) and Nitrogen (-3) require 3 potassiums to balance.

Transition Metals with Polyatomic Ions

• Copper (II) Oxide

  • Formula: CuO
  • Explanation: Copper is +2, Oxygen is -2.

• Iron (II) Phosphide

  • Formula: Fe₃P₂
  • Explanation: Iron is +2, Phosphorus is -3; confirmed by crisscross method.

• Chromium (IV) Nitrate

  • Formula: Cr(NO₃)₄
  • Explanation: Chromium is +4, Nitrate is -1; requires 4 nitrates.

• Cobalt (II) Hydroxide

  • Formula: Co(OH)₂
  • Explanation: Hydroxide is -1; 2 needed to balance Cobalt’s +2.

Polyatomic Ions

• Barium Phosphate

  • Formula: Ba₃(PO₄)₂
  • Explanation: Barium is +2, Phosphate is -3.

• Ammonium Carbonate

  • Formula: (NH₄)₂CO₃
  • Explanation: Ammonium is +1, Carbonate is -2.

Tips for Test

• Remember the charges associated with different groups:
  • Group 1: +1, Group 2: +2, Group 15: -3, Group 16: -2, Group 17: -1.
• Know the transition metals and their potential charges.
• Use the periodic table and the list of polyatomic ions provided during tests.
• No calculator is needed for determining formulas or balancing charges.