Chapter 6.3 – Compound Names and Formulas Naming ions The name of a cation is the same as the name of the element it is an ion of ex. Al 3+ = Na + = Ca 2+ = K + = The name of an anion is the same as the name of the element it is an ion of except the ending changes to –ide ex. Cl - = O 2- = S 2- = F - = N 3- =

Chapter 6.3 – Compound Names and Formulas When naming ionic compounds there are 3 rules to follow: 1.Write the name of the cation first followed by the name of the anion. The amount of each ion does not matter. ex. KCl = CaF 2 = Na 3 N = (NH 4 ) 3 N =

Chapter 6.3 – Compound Names and Formulas 2.When a polyatomic ion is the anion in an ionic compound its name does not change to end with –ide. ex. Mg(NO 3 ) 2 = NaOH = CaSO 4 = (NH 4 ) 2 SO 3 =

Chapter 6.3 – Compound Names and Formulas 3. When the cation is a metal that can have multiple possible charges, the charge must be shown in the name using roman numerals after the cation’s name. The metals that can have multiple possible charges are: iron, copper, lead, cobalt, chromium, mercury, tin, nickel, gold, and manganese To find the charge of the metal ion, figure out the charge of the anion and recall that the total charge of the compound must be 0. ex. CuS = Fe 2 O 3 = FeSO 4 =

Chapter 6.3 – Compound Names and Formulas

There are 7 rules for writing formulas for ionic compounds 1.The total number of positive and negative charges must be equal. Aka the compound must be neutral. 2.Write the symbols side by side with the cation written first. ex. aluminum oxidemagnesium sulfide ammonium phosphidesodium sulfate

Chapter 6.3 – Compound Names and Formulas 3. Cross the charges using the absolute value of each ion’s charge as the subscript for the other ion. Al 3+ O 2- Mg 2+ S 2- NH 4 + P 3- Na + SO Do not write a subscript of 1, it is understood to be there simply by the element being present in the formula.

Chapter 6.3 – Compound Names and Formulas 5. Check the subscripts and divide them by their largest common factor to give them the smallest possible ratio. Do not change the subscripts of polyatomic ions. Al 2 O 3 Mg 2 S 2 (NH 4 ) 3 PNa 2 SO 4 6. If the charges of both ions are the same then no subscripts are needed as the charges will cancel out. Ca 2+ SO 4 2- Fe 3+ P 3-

Chapter 6.3 – Compound Names and Formulas 7.If there is more than one of a specific polyatomic ion in a compound always add parentheses, even if the polyatomic ion does not have a subscript. ammonium sulfateammonium hydroxide

Chapter 6.3 – Compound Names and Formulas