Polyatomic Ion

A charged group of more than one atom bound together A charged group of more than one atom bound together Use the names from the table (pg 257) or from your reference sheet Use the names from the table (pg 257) or from your reference sheet Most end in “-ite” or “-ate” Most end in “-ite” or “-ate” Positive polyatomic ions end in “-ium” Positive polyatomic ions end in “-ium” Examples: Examples: –SO 4 2- = sulfate ion –NO 3 - = nitrate ion –NH 4 + = ammonium ion Polyatomic Ions

Chlorine (Cl) Based Polyatomic Ions ClO 1- ClO 1- ClO 2 1- ClO 2 1- ClO 3 1- ClO 3 1- ClO 4 1- ClO 4 1- Hypochlorite Hypochlorite Chlorite Chlorite Chlorate Chlorate Perchlorate Perchlorate

Sulfur (S) Based Polyatomic Ions HSO 3 1- HSO 3 1- HS HS SO 3 2- SO 3 2- SO 4 2- SO 4 2- Bisulfite (Hydrogen sulfite) Bisulfite (Hydrogen sulfite) Bisulfate (hydrogen sulfate) Bisulfate (hydrogen sulfate) Sulfite Sulfite Sulfate Sulfate

Nitrogen (N) Based Polyatomic Ions NO 2 1- NO 2 1- N N Nitrite Nitrite Nitrate Nitrate

Cyanide (CN 1- )– deadly like Chuck Norris (CN)

Phosphorus (P) Based Polyatomic Ions HPO 4 2- HPO 4 2- H 2 P H 2 P PO 3 3- PO 3 3- PO 4 3- PO 4 3- Biphosphate (Hydrogen phosphate) Biphosphate (Hydrogen phosphate) Dihydrogen Phosphate Dihydrogen Phosphate Phosphite Phosphite Phosphate Phosphate

Chromium (Cr) Based Polyatomic Ions Cr 2 O 7 2- Cr 2 O 7 2- CrO 4 2- CrO 4 2- Dichromate Dichromate Chromate Chromate

Positively Charged Polyatomic Ions H 3 O 1+ H 3 O 1+ NH 4 1+ NH 4 1+ Hydronium Hydronium Ammonium Ammonium

Others C 2 H 3 O 2 1- C 2 H 3 O 2 1- C C C 2 O 4 2- C 2 O 4 2- MnO 4 1- MnO 4 1- Acetate Acetate Carbonate Carbonate Oxalate Oxalate Permanganate Permanganate

Others O 2 2- O 2 2- OH 1- OH 1- Peroxide Peroxide Hydroxide Hydroxide

( ) Example: Barium Nitrate 1. Write the formulas for the cation and anion, including CHARGES! Ba 2+ NO Check to see if charges are balanced. 3. Balance charges, if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced! 2 Writing Ionic Compound Formulas 4. Write the chemical formula (without charges). Ba(NO 3 ) 2

( ) Example: Ammonium Sulfate 1. Write the formulas for the cation and anion, including CHARGES! NH 4 + SO Check to see if charges are balanced. 3. Balance charges, if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced! 2 Writing Ionic Compound Formulas 4. Write the chemical formula (without charges). (NH 4 ) 2 SO 4

Example: Magnesium Carbonate 1. Write the formulas for the cation and anion, including CHARGES! Mg 2+ CO Check to see if charges are balanced. They are balanced! Writing Ionic Compound Formulas 4. Write the chemical formula (without charges). MgCO 3

( ) Example: Zinc Hydroxide 1. Write the formulas for the cation and anion, including CHARGES! Zn 2+ OH - 2. Check to see if charges are balanced. 3. Balance charges, if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced! 2 Writing Ionic Compound Formulas 4. Write the chemical formula (without charges). Zn(OH) 2