Topic: Polyatomic Ions

Essential Questions a.) What is a polyatomic ion? b.) How do you name compounds containing a polyatomic ion. c.) how do you write its formula of a polyatomic ion?

Polyatomic Ion: An ion (either positively or negatively charged) composed of two or more atoms. (NO3)-1 nitrate

Is it possible to predict charges? Charges of polyatomic ions are still based on the overall stability of the molecule Not as predictable as monatomic ions These will have to be memorized (or look at the worksheet) However, this becomes easy with practice

Common Examples HCO32- Bicarbonate Ion PO43- Phosphate Ion NH4+ Ammonium Ion NO3- Nitrate Ion

Naming compounds containing a polyatomic ion Example: NaNO3 If the compound contains a metal cation, the name of the metal comes first. Sodium

Example: NaNO3 2. The second part of the name is just the name of the polyatomic ion Sodium Nitrate

What if the Polyatomic Ion comes first? NH4+ (Ammonium ion) is a positive ion, then write it first NH4Cl – Ammonium chloride

Compounds must be neutral Compounds must be neutral! * If the subscript is not 1, then group the polyatomic ions by using a parenthesis Al2 (SO4)3 (NH4)Cl or NH4Cl

B. How to write formula with polyatomic ions Example: Potassium Carbonate 1. Determine atomic symbols and charges K+ 1 CO32-

Example: Potassium Carbonate 2. Criss Cross the charge K+ 1 CO32-

Example: Potassium Carbonate 2 Example: Potassium Carbonate 2. Determine number of each ion to balance charges 2K+ 1CO32-

Example: Potassium Carbonate 3 Example: Potassium Carbonate 3. Using symbols for both ions and proper subscripts, write the formula K2CO3

Practice Examples 1. BeSO3 2. NaC2H3O2 3. Ca(NO3)2 4. Aluminum Nitrite 5. Iron (II) Hydroxide 6. Ammonium Phosphate