Polyatomic Ions Compounds & Nomenclature

Objectives Covered Today 6. Define a polyatomic ion 7. C4.2c Name compounds containing a polyatomic ion. 8. C4.2d Given the name of a compound containing a polyatomic ion, write its formula.

Objective 6 Define a polyatomic ion Polyatomic Ion: An ion (either positively or negatively charged) composed of two or more atoms.

Is it possible to predict charges? Based on covalent bonding (next chapter) 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 However, this becomes easy with practice

Common Examples HCO 3 2- Bicarbonate Ion PO 4 3- Phosphate Ion NH 4 + Ammonium Ion NO 3 - Nitrate Ion

Objective 7 Name compounds containing a polyatomic ion Example: NaNO 3 1.If the compound contains a metal cation, the name of the metal comes first.

Objective 7 Name compounds containing a polyatomic ion Example: NaNO 3 1.If the compound contains a metal cation, the name of the metal comes first. Sodium

Objective 7 Name compounds containing a polyatomic ion Example: NaNO 3 2. The second part of the name is just the name of the polyatomic ion Sodium

Objective 7 Name compounds containing a polyatomic ion Example: NaNO 3 2. The second part of the name is just the name of the polyatomic ion Sodium Nitrate

What if the Polyatomic Ion comes first? NH 4 + (Ammonium ion) is a positive ion while still being polyatomic If you are using a polyatomic cation you just use the ion’s name, and it will be written first NH 4 Cl

What if more than one Polyatomic Ion is needed? Compounds must be neutral! If > 1 polyatomic ion is needed in a formula, it will be put in parentheses before the subscript When writing its name, it will just remain the name of the polyatomic ion Al 2 (SO 4 ) 3

Objective 8 Given the name of a compound containing a polyatomic ion, write its formula. Example: Potassium Carbonate 1. Determine atomic symbols and charges

Objective 8 Given the name of a compound containing a polyatomic ion, write its formula. Example: Potassium Carbonate 1. Determine atomic symbols and charges K + CO 3 2-

Objective 8 Given the name of a compound containing a polyatomic ion, write its formula. Example: Potassium Carbonate 2. Determine number of each ion to balance charges K + CO 3 2-

Objective 8 Given the name of a compound containing a polyatomic ion, write its formula. Example: Potassium Carbonate 2. Determine number of each ion to balance charges 2K + 1CO 3 2-

Objective 8 Given the name of a compound containing a polyatomic ion, write its formula. Example: Potassium Carbonate 3. Using symbols for both ions and proper subscripts, write the formula K 2 CO 3

Practice Examples 1. BeSO 3 2. NaC 2 H 3 O 2 3. Ca(NO 3 ) 2 4. Aluminum Nitrite 5. Iron (II) Hydroxide 6. Ammonium Phosphate

Happy Thanksgiving Break!