Ionic Bonding with Polyatomic Ions Recall: Recall: “Poly” = many or more than one “Poly” = many or more than one “Atomic” = atom or atoms “Atomic” = atom or atoms “Polyatomic Ion” “Polyatomic Ion” More than one atom stuck together with a single ionic charge More than one atom stuck together with a single ionic charge Act as a single unit  they are permanently stuck together with a charge Act as a single unit  they are permanently stuck together with a charge Found on the back side of your periodic table Found on the back side of your periodic table

Familiarizing yourself with Polyatomic Ions Provide the formula for the following polyatomic ions: Provide the formula for the following polyatomic ions: Sulfate Sulfate SO 4 2- SO 4 2- Nitrite Nitrite NO 2 - NO 2 - Dichromate Dichromate Cr 2 O 7 2- Cr 2 O 7 2- Provide the name for the following polyatomic ions: Provide the name for the following polyatomic ions: ClO 3 - ClO 3 - Chlorate Chlorate NO 3 - NO 3 - Nitrate Nitrate PO 4 3- PO 4 3- Phosphate Phosphate

Naming Ionic Compounds with Polyatomic Ions Step 1: The cation is STILL always named first Step 1: The cation is STILL always named first Even if it is a polyatomic cation, it still gets named first Even if it is a polyatomic cation, it still gets named first Cations say their own name Cations say their own name Even polyatomic cations say their own name Even polyatomic cations say their own name

Naming Ionic Compounds with Polyatomic Ions Step 2: Anions are ALWAYS named second Step 2: Anions are ALWAYS named second Even polyatomic anions are named second Even polyatomic anions are named second If the anion is monoatomic, change its ending suffix to “ide” If the anion is monoatomic, change its ending suffix to “ide” If the anion is polyatomic, it keeps its own name If the anion is polyatomic, it keeps its own name

Naming Ionic Compounds with Polyatomic Ions SO, as a general rule of thumb… no matter what – cation or anion – POLYATOMIC IONS ALWAYS KEEP THEIR OWN NAME! SO, as a general rule of thumb… no matter what – cation or anion – POLYATOMIC IONS ALWAYS KEEP THEIR OWN NAME!

Naming Ionic Compounds with Polyatomic Ions Examples: Examples: Ammonium & chlorine Ammonium & chlorine Ammonium = poylatomic cation Ammonium = poylatomic cation Chlorine = monoatomic anion Chlorine = monoatomic anion  Ammonium chloride  Ammonium chloride Potassium & sulfate Potassium & sulfate Potassium = monoatomic cation Potassium = monoatomic cation Sulfate = polyatomic anion Sulfate = polyatomic anion  Potassium sulfate  Potassium sulfate Lead (2+) & phosphate Lead (2+) & phosphate Lead (2+) = monoatomic cation Lead (2+) = monoatomic cation Phosphate = polyatomic anion Phosphate = polyatomic anion  Lead (II) phosphate  Lead (II) phosphate Ammonium & oxalate Ammonium & oxalate Ammonium = polyatomic cation Ammonium = polyatomic cation Oxalate = polyatomic anion Oxalate = polyatomic anion  Ammonium oxalate  Ammonium oxalate

Writing Formulas with Polyatomic Ions Step 1. Use the front and back side of the periodic table to determine the symbols and the charges of the ions involved Step 1. Use the front and back side of the periodic table to determine the symbols and the charges of the ions involved Remember, polyatomic ions act as a SINGLE unit Remember, polyatomic ions act as a SINGLE unit The charge applies to all of the atoms in that unit The charge applies to all of the atoms in that unit To remind yourself of this, place brackets around the atoms of a polyatomic ion and leave the charge outside of the brackets To remind yourself of this, place brackets around the atoms of a polyatomic ion and leave the charge outside of the brackets i.e. – Sulfate = (SO 4 ) 2- i.e. – Sulfate = (SO 4 ) 2- The entire group of atoms in sulfate have an overall charge of 2- The entire group of atoms in sulfate have an overall charge of 2- i.e. Ammonium & chlorine  (NH 4 )+ & Cl- i.e. Ammonium & chlorine  (NH 4 )+ & Cl-  (NH 4 )Cl  (NH 4 )Cl i.e. Iron (2+) & nitrate  Fe 2+ & (NO 3 )- i.e. Iron (2+) & nitrate  Fe 2+ & (NO 3 )-  Fe(NO 3 ) 2  Fe(NO 3 ) 2

Writing Formulas with Polyatomic Ions Step 2. Make sure that the “positives” equal the “negatives”. Step 2. Make sure that the “positives” equal the “negatives”. Same process as binary ionic compounds  simply cross the charges and make them subscripts Same process as binary ionic compounds  simply cross the charges and make them subscripts When working with polyatomic ions, ALWAYS cross the charges OUTSIDE OF THE BRACKETS! When working with polyatomic ions, ALWAYS cross the charges OUTSIDE OF THE BRACKETS! Remember the atoms of a polyatomic ion act as a single unit, so NEVER change the subscripts inside a bracket Remember the atoms of a polyatomic ion act as a single unit, so NEVER change the subscripts inside a bracket i.e. Ammonium & chlorine  (NH 4 )+ & Cl- i.e. Ammonium & chlorine  (NH 4 )+ & Cl-  (NH 4 )Cl  (NH 4 )Cl i.e. Iron (2+) & nitrate  Fe 2+ & (NO 3 ) - i.e. Iron (2+) & nitrate  Fe 2+ & (NO 3 ) -  Fe(NO 3 ) 2  Fe(NO 3 ) 2

Tricky Rules When an ion has a charge of (+1) or (- 1), there is no need to include it as a subscript When an ion has a charge of (+1) or (- 1), there is no need to include it as a subscript i.e.: Ammonium & chlorine = (NH 4 )Cl, not (NH 4 ) 1 Cl 1 i.e.: Ammonium & chlorine = (NH 4 )Cl, not (NH 4 ) 1 Cl 1 Make sure to still use roman numerals for transition metals! Make sure to still use roman numerals for transition metals! When a compound has two subscripts that are both even numbers, we want to reduce them to the lowest ratio possible When a compound has two subscripts that are both even numbers, we want to reduce them to the lowest ratio possible *For polyatomic ions you can only reduce subscripts found OUTSIDE of the brackets!* *For polyatomic ions you can only reduce subscripts found OUTSIDE of the brackets!* DO NOT CHANGE ANYTHING INSIDE THE BRACKETS! DO NOT CHANGE ANYTHING INSIDE THE BRACKETS! i.e.: Lead (2+) & Sulfate i.e.: Lead (2+) & Sulfate  Pb(SO 4 ), not Pb 2 (SO 4 ) 2, not Pb(SO 2 ), not Pb(SO)  Pb(SO 4 ), not Pb 2 (SO 4 ) 2, not Pb(SO 2 ), not Pb(SO) i.e.: Lead (4+) & Sulfate i.e.: Lead (4+) & Sulfate  Pb(SO 4 ) 2, not Pb(SO 2 ), not Pb(SO 2 ) 2  Pb(SO 4 ) 2, not Pb(SO 2 ), not Pb(SO 2 ) 2

More Examples: Potassium & Carbonate Potassium & Carbonate Name = potassium carbonate Name = potassium carbonate Formula = K 2 (CO 3 ) Formula = K 2 (CO 3 ) Iron (2+) & Nitrate Iron (2+) & Nitrate Name = iron (II) nitrate Name = iron (II) nitrate Formula = Fe(NO 3 ) 2 Formula = Fe(NO 3 ) 2 Ammonium & Sulfur Ammonium & Sulfur Name = ammonium sulfide Name = ammonium sulfide Formula = (NH 4 ) 2 S Formula = (NH 4 ) 2 S Sodium & Sulfate Sodium & Sulfate Name = sodium sulfate Name = sodium sulfate Formula = Na 2 (SO 4 ) Formula = Na 2 (SO 4 ) Aluminum & Phosphate Aluminum & Phosphate Name = Aluminum phosphate Name = Aluminum phosphate Formula = Al(PO 4 ) Formula = Al(PO 4 )