Ionic Nomenclature

Naming Ions and Ionic Compounds Name to Formula 1. Write the cation first (include charge) 2. Write the anion second (include charge) 3. “Swap and drop” the charges to determine how many of each ion are needed 4. Make sure the total charge of the compound is 0 (The final formula will NOT have + or – in it.) 5. Rewrite the formula without charges

Example: Lithium oxide 1. Cation (including charge): Li+ 2. Anion (including charge): O2- 3. Swap and drop charges: Li+ O2- Li+2 O2- 1 Li2O “Oxide” ends in –ide and is not found on the polyatomic ion chart. We know the charge is 2- because of where oxygen is found on the periodic table. The formula is neutral: Li: +1 x 2 = +2 charge O: -2 x 1 = -2 charge 0 total charge There is are two lithium cations and one oxide anion.

Example: Barium nitrate 1. Cation (including charge): Ba2+ 2. Anion (including charge): NO3- 3. Swap and drop charges: Ba2+ NO3- Ba2+1 NO3- 2 Ba(NO2)2 “Nitrate” is a polyatmic ion whose name you should have memorized. The formula is neutral: Ba: +2 x 1 = +2 charge NO3: -1 x 2 = -2 charge 0 total charge There is one barium cation and two nitrate anions. The parentheses show that there are two nitrate ions.

Example: Aluminum sulfate 1. Cation (including charge): Al3+ 2. Anion (including charge): SO42- 3. Swap and drop charges: Al3+ SO42- Al3+ 2 SO42- 3 Al2 (SO4)3 “Sulfate” is a polyatmic ion whose name you should have memorized. The formula is neutral: Al: +3 x 2 = +6 charge SO4: -2 x 3 = -6 charge 0 total charge There are two aluminum cations and three sulfate anions. The parentheses show that there are three sulfate ions.

Example: Sodium chloride 1. Cation (including charge): Na+ 2. Anion (including charge): Cl- 3. Swap and drop charges: Na+ Cl- Na+1 Cl-1 NaCl “Chloride” ends in –ide and is not found on the polyatomic ion chart. We know the charge is 1- because of where chlorine is found on the periodic table. The formula is neutral: Na: +1 x 1 = +1 charge Cl: -1 x 1 = -1 charge 0 total charge There is one sodium cation and one chloride anion.

Example: Aluminum oxide 1. Cation (including charge): Al3+ 2. Anion (including charge): O2- 3. Swap and drop charges: Al3+ O2- Al3+ 2 O2- 3 Al2 O3 “Oxide” ends in –ide and is not found on the polyatomic ion chart. We know the charge is 2- because of where oxygen is found on the periodic table. The formula is neutral: Al: +3 x 2 = +6 charge O: -2 x 3 = -6 charge 0 total charge There are two aluminum cations and three oxide anions.

Example: Ammonium nitrate 1. Cation (including charge): NH4+ 2. Anion (including charge): NO3- 3. Swap and drop charges: NH4+ NO3- NH4+1 NO3- 1 NH4NO3 “Ammonium” and “nitrate” are polyatmic ions whose names you should have memorized. The formula is neutral: NH4: +1 x 1 = +1 charge NO3: -1 x 1 = -1 charge 0 total charge There is one ammonium cation and one nitrate anion. Parentheses are not needed because there is only one of each polyatomic ion.

Example: Calcium hydroxide 1. Cation (including charge): Ca2+ 2. Anion (including charge): OH- 3. Swap and drop charges: Ca2+ OH- Ca2+1 OH- 2 Ca(OH)2 “Hydrocide” is a polyatmic ion whose name you should have memorized. The formula is neutral: Ca: +2 x 1 = +2 charge OH: -1 x 2 = -2 charge 0 total charge There is one calcium cation and two hydroxide anions. The parentheses show that there are two hydroxide ions.

Example: Barium chloride “Chloride” ends in –ide and is not found on the polyatomic ion chart. We know the charge is 1- because of where chlorine is found on the periodic table. Barium chloride 1. Cation (including charge): Ba2+ 2. Anion (including charge): Cl- 3. Swap and drop charges: Ba2+ Cl- Ba2+1 Cl- 2 BaCl2 The formula is neutral: Ba: +2 x 1 = +2 charge Cl: -1 x 2 = -2 charge 0 total charge There is one barium cation and two chloride anions.

Example: Magnesium oxide 1. Cation (including charge): Mg2+ 2. Anion (including charge): O2- 3. Swap and drop charges: Mg2+ O2- Mg2+2 O2-2 Mg2O2 MgO “Oxide” ends in –ide and is not found on the polyatomic ion chart. We know the charge is 2- because of where oxygen is found on the periodic table. The formula is neutral: Mg: +2 x 2 = +4 charge Cl: -2 x 2 = -4 charge 0 total charge The smallest possible ratio is 1:1, not 2:2. There is one magnesium cation and one oxide anion.

Example: Lead (II) nitride The Roman numeral tells us that lead has a charge of +2. “Nitride” ends in –ide and is not found on the polyatomic ion chart. We know the charge is -3 because of where nitrogen is found on the periodic table. Lead (II) nitride 1. Cation (including charge): Pb2+ 2. Anion (including charge): N3- 3. Swap and drop charges: Pb2+ N3- Pb2+3 N3- 2 Pb3N2 The formula is neutral: Pb: +2 x 3 = +6 charge N: -3 x 2 = -6 charge 0 total charge There are three lead (II) cations and two nitride anions.

Naming Ions and Ionic Compounds Formula to Name 1. Determine the charge of the cation (+) 2. Determine the charge of the anion (-) 3. Write the name of the cation Use element name or polyatomic cation name Include Roman numeral if necessary D-block NOT Ag+, Cd2+, or Zn2+ 4. Write the name of the anion -ide or from the polyatomic ion chart

Example: Sr(ClO2)2 Sr(ClO2)2 Strontium chlorite Anion charge: ClO2 has a charge of -1. It is a polyatomic ion. There are two of them so the -1 charge balances out the 2+ charge of Sr2+. Name: Chlorite Cation charge: Sr has a charge of 2+. We know this because it is located in Group 2 on the periodic table. Name: Strontium Sr(ClO2)2 Strontium chlorite Strontium does NOT need a Roman numeral because it is found in the s-block. Only d-block elements and some p-block elements need Roman numerals.

Example: CuCl CuCl Copper (I) chloride Anion charge: Cl has a charge of -1. We know this because it is located in Group 17 on the periodic table. The name will end in –ide. Name: Chloride Cation charge: Cu is found in the d-block and can form more than one ion. Its charge in this compound will be +1 to balance Cl-. Name: Copper (I) CuCl Copper (I) chloride Copper DOES need a Roman numeral because it is found in the d-block. The +1 charge tells us what Roman numeral to use.

Example: Pb(NO3)2 Pb(NO3)2 Lead (II) nitrate Anion charge: NO3 has a charge of -1. It is a polyatomic ion. There are TWO of them for a total negative charge of -2. Name: Nitrate Cation charge: Pb is found in the lower-left p-block and can form more than one ion. Its charge in this compound will be +2 to balance the two NO3- ions. Name: Lead (II) Pb(NO3)2 Lead (II) nitrate Lead DOES need a Roman numeral because it is found in the lower-left p-block. The +2 charge tells us what Roman numeral to use.

Example: Pb(NO3)3 Pb(NO3)3 Lead (III) nitrate Anion charge: NO3 has a charge of -1. It is a polyatomic ion. There are THREE of them for a total negative charge of -3. Name: Nitrate Cation charge: Pb is found in the lower-left p-block and can form more than one ion. Its charge in this compound will be +3 to balance the two NO3- ions. Name: Lead (III) Pb(NO3)3 Lead (III) nitrate Lead DOES need a Roman numeral because it is found in the lower-left p-block. The +3 charge tells us what Roman numeral to use.

Example: KI KI Potassium Iodide Anion charge: I has a charge of -1. We know this because it is located in Group 17 on the periodic table. The name will end in –ide. Name: Iodide Cation charge: K has a charge of +1. We know this because it is located in Group 1 on the periodic table. Name: Potassium KI Potassium Iodide Potassium does NOT need a Roman numeral because it is found in the s-block. Only d-block elements and some p-block elements need Roman numerals.