We’ll go over the method of naming ionic compounds that have one or more polyatomic ions.

Any time a formula has more than two elements in it, or more than two capital letters,

it must contain at least one polyatomic ion. Any time a formula has more than two elements in it, or more than two capital letters, it must contain at least one polyatomic ion.

Lets consider the formula MgSO4, MgSO 4 Al(NO 3 ) 3 NH 4 ClO 3

It has 3 elements in it: magnesium, sulphur, and oxygen, so it must contain a polyatomic ion. Al(NO 3 ) 3 NH 4 ClO 3 3 Elements MgSO 4

The polyatomic ions that we’ll be using in this course are shaded on this table. If we are given a formula with more than 2 elements in it, we look on this table for any polyatomic ions that are in the formula. Formulas and Charges of Common Ions

The formula we’re working with is MgSO4, Formulas and Charges of Common Ions MgSO 4

SO4 in the formula (click) is from the polyatomic ion sulphate, SO4 2 minus Formulas and Charges of Common Ions MgSO 4

Mg in the formula is from (click) the single metal ion Mg 2+ Formulas and Charges of Common Ions MgSO 4

So MgSO4 contains the polyatomic ion sulphate, SO4. Al(NO 3 ) 3 NH 4 ClO 3 Polyatomic Ion MgSO 4

Now we’ll consider the formula Al, NO3 in brackets, 3 MgSO 4 NH 4 ClO 3 Al(NO 3 ) 3

This formula also contains 3 elements, (click) aluminum, nitrogen, and oxygen. So it must have a polyatomic ion in it. MgSO 4 NH 4 ClO 3 Al(NO 3 ) 3 3 Elements

The formula we’re working with is Al(NO 3 ) 3 Formulas and Charges of Common Ions Al(NO 3 ) 3

We see that NO3 in the formula (click) is from the polyatomic ion nitrate, NO3 minus. Formulas and Charges of Common Ions Al(NO 3 ) 3

And The Al in the formula Formulas and Charges of Common Ions Al(NO 3 ) 3

Is from the single metal ion Al 3plus Formulas and Charges of Common Ions Al(NO 3 ) 3

So Al(NO3)3 contains the polyatomic ion nitrate NO3 MgSO 4 NH 4 ClO 3 Al(NO 3 ) 3 Polyatomic Ion

We see that this formula contains 4 elements: (click) Nitrogen, hydrogen, chlorine, and oxygen MgSO 4 NH 4 ClO 3 4 Elements

NH 4 ClO 3 The formula we’re working with is NH 4 ClO 3. Formulas and Charges of Common Ions

NH 4 ClO 3 Looking on the table, we see that NH4 in the formula, Formulas and Charges of Common Ions

NH 4 ClO 3 Comes from the positive polyatomic ion ammonium, NH4 plus Formulas and Charges of Common Ions

NH 4 ClO 3 And ClO3 in the formula Formulas and Charges of Common Ions

NH 4 ClO 3 Comes from the negative polyatomic ion chlorate, ClO3 minus Formulas and Charges of Common Ions

So the formula NH4ClO3 contains 2 polyatomic ions, (click) NH4 or ammonium, and ClO3, or chlorate. MgSO 4 NH 4 ClO 3 2 Polyatomic Ions

Now that we’ve shown you how to find polyatomic ions in formulas, lets look at the rules for naming compounds with polyatomic ions. Rules for Naming Compounds with Polyatomic Ions

The first rule is, the name of a polyatomic ion does not change in any way when it is used in a compound name. Its name is the same in a compound as it is on an ion table. Rules for Naming Compounds with Polyatomic Ions 1.The name of a polyatomic ion does not change when it is used in a compound name. 2.Single elements follow the same naming rules as they do in other compounds.

The second rule is, single elements that are not in polyatomic ions, follow the same rules as they do in other compounds. Rules for Naming Compounds with Polyatomic Ions 1.The name of a polyatomic ion does not change when it is used in a compound name. 2.Single elements follow the same naming rules as they do in other compounds.

The best way to learn how to name compounds with polyatomic ions, is to see several examples. Here, we’re asked to name the compound NH 4 Br Name the compound with the formula NH 4 Br

We see that NH4Br has 3 elements (click) nitrogen, hydrogen, and bromine. Therefore, it must contain a polyatomic ion. NH 4 Br 3 Elements Name the compound with the formula NH 4 Br

NH 4 Br Looking on the table, we see that NH4 in the formula, Name the compound with the formula NH 4 Br

NH 4 Br Is from the polyatomic ion ammonium, NH4 plus. Name the compound with the formula NH 4 Br

Names of polyatomic ions don’t change when they are part of a compound name, so the first part of the name (click), is ammonium. NH 4 Br ammonium bromide Name the compound with the formula NH 4 Br

The formula ends with the single element Br NH 4 Br ammonium bromide ine Name the compound with the formula NH 4 Br

Which the periodic table tells us is bromine. NH 4 Br ammonium bromide ine Name the compound with the formula NH 4 Br

So we’ll note down bromine here. NH 4 Br ammonium bromide ine Name the compound with the formula NH 4 Br

But for a non-metal element at the end of a formula, the name must be changed to end in –ide. Name the compound with the formula NH 4 Br NH 4 Br ammonium bromide ine For a non-metal at the end of a formula, the name ends in “ide”

So we replace the “ine” with “ide” Name the compound with the formula NH 4 Br NH 4 Br ammonium bromide ine ide

And we’re left with the name bromide. Name the compound with the formula NH 4 Br NH 4 Br ammonium bromide ide

Alternately, we can find Br minus on the ion table, and we see that it’s name is bromide, so if a non-metal ion is on our ion table, we can just copy the name directly from there. Name the compound with the formula NH 4 Br NH 4 Br ammonium bromide ide On the ion table

So the final answer is (click) the name of this compound is ammonium bromide Name the compound with the formula NH 4 Br NH 4 Br ammonium bromide ide