Polyatomic Ions

Definition

• Polyatomic Ion: A group of atoms that has a charge.
  • Example of individual ions: Na⁺, Mg²⁺, O^2-.
  • Formed by two or more atoms that collectively have a charge.

Examples of Polyatomic Ions

1. Nitrate (NO₃^-)

   • 1 Nitrogen + 3 Oxygens
   • Overall charge: -1

2. Ammonium (NH₄⁺)

   • 1 Nitrogen + 4 Hydrogens
   • Total protons = 11; Total electrons = 10
   • Net charge: +1 (more protons than electrons)
   • Structure: [NH₄]⁺ (indicating positive charge)
   • Class: Cation (positive ion)

3. Carbonate (CO₃^2-)

   • 1 Carbon + 3 Oxygens
   • Total protons = 30; Total electrons = 32
   • Net charge: -2 (more electrons than protons)
   • Structure: [CO₃]^2- (indicating negative charge)
   • Class: Anion (negative ion)

Importance

• Polyatomic ions are essential for writing chemical formulas of compounds.
• Memorization is crucial due to their frequent use in chemistry.

Learning Resources

• Video: Learning Polyatomic Ions
  • Offers strategies for memorization.
• Video: How Are Polyatomic Ions Made?
  • Discusses the covalent and ionic bonding involved in the formation of polyatomic ions.

Summary

• Polyatomic ions are groups of atoms that can have either a net positive or negative charge due to the imbalance of protons and electrons.