Naming Ionic Compounds With Polyatomic Ions

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Chemistry - Naming Ionic Compounds with Polyatomic Ions
A. Chemical Name to Chemical Formula

1. Write down the symbol(s) and charge of cation, then the anion.

2a. The number of positive ions has to equal the number of negative ions.

2b. Determine the number of each ion to make the charges equal.

3. To get correct chemical formula

Each # of ions will be the subscript of the ion in the final chemical formula.
When writing chemical formula, never shows charges of ions.
All polyatomic ions need to have parentheses around them and a subscript (even if it is 1).

Example: Sodium sulfate
Step 1 Na¹⁺ SO₄^2-
Step 2 Need two cations, Na¹⁺, Na¹⁺,and one anion, SO₄^2-
Step 3 Na₂(SO₄)₁

More Examples: Magnesium nitrate, Ammonium phosphate {Answer: Mg₁(NO₃)₂, (NH₄)₃(PO₄)₁}

B. Chemical Formula to Chemical Name

1. Write down the chemical name for the cation (always first part). (it will be the first word, 1st letter is capitalized).

2. Write down the chemical name for the anion (always second part). (it will be second word, Never Capitalized).

Example: Ca₁(OH)₂
Step 1 Calcium
Step 2 Calcium hydroxide
More Example: Li₂(SO₃)₁ (Answer: Lithium sulfite)