Polyatomic Ions and Ionic Compounds
Polyatomic ions are charged particles made of multiple atoms that act as a single unit. Some common ones include ammonium (NH₄⁺), hydroxide (OH⁻), nitrate (NO₃⁻), and sulfate (SO₄²⁻). You'll need to memorize these for your chemistry class!
When forming ionic compounds, we combine positive ions (cations) and negative ions (anions) to create neutral compounds. The key is to balance the charges. For example, when combining sodium (Na⁺) with hydroxide (OH⁻), we get NaOH because the charges balance out .
For ions with multiple charges, we need to adjust the ratios. When magnesium (Mg²⁺) combines with acetate (C₂H₃O₂⁻), we need two acetate ions to balance magnesium's 2+ charge, giving us Mg(C₂H₃O₂)₂. The parentheses indicate that the entire polyatomic ion repeats.
💡 Quick Tip: When forming ionic compounds, cross the charges to find the subscripts. For example, Ca²⁺ and Cl⁻ form CaCl₂ because you need two Cl⁻ ions to balance the 2+ charge.
