Polyatomic Ions Compounds Nomenclature Naming Objectives Define a

Polyatomic Ions Compounds & Nomenclature (Naming)

Objectives • Define a polyatomic ion • Name compounds containing a polyatomic ion. • Given the name of a compound containing a polyatomic ion, write its formula.

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 unit) • 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 use page 9 in your CRM • This becomes easier with practice

Common Examples HCO 32 - Bicarbonate Ion PO 43 - Phosphate Ion NH 4+ Ammonium Ion NO 3 - Nitrate Ion

Name compounds containing a polyatomic ion Example: Na. NO 3 1. If the compound contains a metal cation, the name of the metal comes first.

Name compounds containing a polyatomic ion Example: Na. NO 3 1. If the compound contains a metal cation, the name of the metal comes first. Sodium

Name compounds containing a polyatomic ion Example: Na. NO 3 2. The second part of the name is just the name of the polyatomic ion Sodium

Name compounds containing a polyatomic ion Example: Na. NO 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 Ammonium chloride

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 Aluminum sulfate

Steps of Naming Polyatomic Compounds and Formula Writing Given the name of a compound containing a polyatomic ion, write its formula. Example: Potassium Carbonate 1. Determine atomic symbols and charges

Given the name of a compound containing a polyatomic ion, write its formula. Example: Potassium Carbonate 1. Determine atomic symbols and charges K+ CO 32 -

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 32 -

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 2 K+ 1 CO 32 -

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. Be. SO 3 2. Na. C 2 H 3 O 2 3. Ca(NO 3)2 4. Aluminum Nitrite 5. Iron (II) Hydroxide 6. Ammonium Phosphate