In the video, you learned that the names and formulas for ternary ionic compounds are written using a process similar to that for binary ionic compounds.
Keep in mind
In ternary ionic compounds the polyatomic ion behaves as a unit, so never change the subscripts of the atoms within the ion. Also, if more than one ion is needed, place parentheses around the ion and write the subscript outside of the parentheses.
Let's Practice
Practice writing formulas for ternary ionic compounds by completing this activity. Determine the chemical formula for the compound on each tab and then check your answers.
If you need a periodic table, click below to open an interactive periodic table or to download a PDF.
Write the chemical formula for the compound formed between calcium and chlorate.
Ca(ClO3)2
If you need help arriving at this answer, click the Solution button.
| Step 1: Write the symbols and charge of each ion. | Ca2+ ClO3− |
| Step 2: Criss-cross the charges, dropping ones and signs, so each charge becomes the other ion's subscript. |
Ca (ClO3)2 Remember to put parenthesis around the polyatomic ion when there is an added subscript for the polyatomic ion. |
| Step 3: Reduce and simplify, if necessary. | Ca(ClO3)2 |
Write the chemical formula for lead (IV) sulfate.
Pb(SO4)2
If you need help arriving at this answer, click the Solution button.
| Step 1: Write the symbols and charge of each ion. | Pb4+ SO42− |
| Step 2: Criss-cross the charges, dropping ones and signs, so each charge becomes the other ion's subscript. |
Pb2 (SO4)4 Remember to put parenthesis around the polyatomic ion when there is an added subscript for the polyatomic ion. |
| Step 3: Reduce and simplify, if necessary. |
Reduce by greatest common factor, which is 2. Pb(SO4)2 |
Write the chemical formula for copper (II) hydroxide.
Cu(OH)2
If you need help arriving at this answer, click the Solution button.
| Step 1: Write the symbols and charge of each ion. | Cu2+ OH− |
| Step 2: Criss-cross the charges, dropping ones and signs, so each charge becomes the other ion's subscript. |
Cu (OH)2 Remember to put parenthesis around the polyatomic ion when there is an added subscript for the polyatomic ion. |
| Step 3: Reduce and simplify, if necessary. | Cu (OH)2 |
Now test your understanding of ternary ionic compounds by answering these questions.
What is the formula for calcium phosphate?
- Ca2PO4
- CaPO2
- Ca2PO3
- Ca3(PO4)2
To write the formula for a ternary ionic compound, criss-cross the charges, ignoring signs and ones. Remember to put parentheses around the polyatomic ion when there is an added subscript.
To write the formula for a ternary ionic compound, criss-cross the charges, ignoring signs and ones. Remember to put parentheses around the polyatomic ion when there is an added subscript.
To write the formula for a ternary ionic compound, criss-cross the charges, ignoring signs and ones. Remember to put parentheses around the polyatomic ion when there is an added subscript.
To write the formula for a ternary ionic compound, criss-cross the charges, ignoring signs and ones. Remember to put parentheses around the polyatomic ion when there is an added subscript.
What is the name of Mn(CO3)2?
- manganese carbonate
- manganese (II) carbonate
- manganese (IV) carbonate
- manganese (VI) carbonate
To name a ternary ionic compound, name the metal cation followed by the polyatomic anion. Remember that transition metal cations require a Roman numeral to represent their charge in the compound. Because carbonate has a charge of 2- and there are two carbonate ions present in this compound, manganese must have a 4+ charge, which is represented by a Roman numeral 4, IV.
To name a ternary ionic compound, name the metal cation followed by the polyatomic anion. Remember that transition metal cations require a Roman numeral to represent their charge in the compound. Because carbonate has a charge of 2- and there are two carbonate ions present in this compound, manganese must have a 4+ charge, which is represented by a Roman numeral 4, IV.
To name a ternary ionic compound, name the metal cation followed by the polyatomic anion. Remember that transition metal cations require a Roman numeral to represent their charge in the compound. Because carbonate has a charge of 2- and there are two carbonate ions present in this compound, manganese must have a 4+ charge, which is represented by a Roman numeral 4, IV.
To name a ternary ionic compound, name the metal cation followed by the polyatomic anion. Remember that transition metal cations require a Roman numeral to represent their charge in the compound. Because carbonate has a charge of 2- and there are two carbonate ions present in this compound, manganese must have a 4+ charge, which is represented by a Roman numeral 4, IV.
How many nitrate ions are in a formula unit for the compound magnesium nitrate?
- 1
- 2
- 4
- 6
The added subscript on a polyatomic ion in the formula of a ternary ionic compound indicates how many of that ion are present in the compound. The formula for magnesium nitrate is Mg(NO3)2.
The added subscript on a polyatomic ion in the formula of a ternary ionic compound indicates how many of that ion are present in the compound. The formula for magnesium nitrate is Mg(NO3)2.
The added subscript on a polyatomic ion in the formula of a ternary ionic compound indicates how many of that ion are present in the compound. The formula for magnesium nitrate is Mg(NO3)2.
The added subscript on a polyatomic ion in the formula of a ternary ionic compound indicates how many of that ion are present in the compound. The formula for magnesium nitrate is Mg(NO3)2.
What is the formula for aluminum chlorite?
- AlClO3
- Al(ClO2)3
- AlClO6
- AlClO2
To write the formula of an ionic compound, criss-cross the charges, ignoring signs and ones. Aluminum is a Group 13 metal, so it forms a 3+ ion. Chlorite is a polyatomic ion with the formula ClO21-. Remember to put parentheses around the polyatomic ion when there is an added subscript.
To write the formula of an ionic compound, criss-cross the charges, ignoring signs and ones. Aluminum is a Group 13 metal, so it forms a 3+ ion. Chlorite is a polyatomic ion with the formula ClO21-. Remember to put parentheses around the polyatomic ion when there is an added subscript.
To write the formula of an ionic compound, criss-cross the charges, ignoring signs and ones. Aluminum is a Group 13 metal, so it forms a 3+ ion. Chlorite is a polyatomic ion with the formula ClO21-. Remember to put parentheses around the polyatomic ion when there is an added subscript.
To write the formula of an ionic compound, criss-cross the charges, ignoring signs and ones. Aluminum is a Group 13 metal, so it forms a 3+ ion. Chlorite is a polyatomic ion with the formula ClO21-. Remember to put parentheses around the polyatomic ion when there is an added subscript.
What is the name of K3PO3?
- potassium phosphate
- potassium (III) phosphate
- potassium phosphite
- potassium (III) phosphite
To name a ternary ionic compound, name the metal cation followed by the polyatomic anion. Remember that Roman numerals are only required for transition metal cations.
To name a ternary ionic compound, name the metal cation followed by the polyatomic anion. Remember that Roman numerals are only required for transition metal cations.
To name a ternary ionic compound, name the metal cation followed by the polyatomic anion. Remember that Roman numerals are only required for transition metal cations.
To name a ternary ionic compound, name the metal cation followed by the polyatomic anion. Remember that Roman numerals are only required for transition metal cations.
What is the formula for sodium sulfite?
- NaSO3
- Na2SO3
- Na2(SO3)
- Na(SO)3
To write the formula for an ionic compound, criss-cross the charges, ignoring signs and ones. Parentheses are only necessary when the added subscript on a polyatomic ion is greater than one.
To write the formula for an ionic compound, criss-cross the charges, ignoring signs and ones. Parentheses are only necessary when the added subscript on a polyatomic ion is greater than one.
To write the formula for an ionic compound, criss-cross the charges, ignoring signs and ones. Parentheses are only necessary when the added subscript on a polyatomic ion is greater than one.
To write the formula for an ionic compound, criss-cross the charges, ignoring signs and ones. Parentheses are only necessary when the added subscript on a polyatomic ion is greater than one.
How many ammonium ions are present in a formula unit of ammonium bromide?
- 1
- 2
- 3
- 4
The formula for ammonium bromide is NH4Br. The added subscript on a polyatomic ion formula indicates how many of that ion are present in the compound. In this example, the added subscript on ammonium is 1 (criss-crossed from the charge of bromide). The 4 is part of the formula for ammonium (NH4+).
The formula for ammonium bromide is NH4Br. The added subscript on a polyatomic ion formula indicates how many of that ion are present in the compound. In this example, the added subscript on ammonium is 1 (criss-crossed from the charge of bromide). The 4 is part of the formula for ammonium (NH4+).
The formula for ammonium bromide is NH4Br. The added subscript on a polyatomic ion formula indicates how many of that ion are present in the compound. In this example, the added subscript on ammonium is 1 (criss-crossed from the charge of bromide). The 4 is part of the formula for ammonium (NH4+).
The formula for ammonium bromide is NH4Br. The added subscript on a polyatomic ion formula indicates how many of that ion are present in the compound. In this example, the added subscript on ammonium is 1 (criss-crossed from the charge of bromide). The 4 is part of the formula for ammonium (NH4+).
Summary
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