Lesson 5 Ionic Compounds - Naming and Formulas
Formulas of Compounds That Contain Polyatomic Ions
Did you know that the pyramids of Giza are made from limestone?
B5.8 The Great Sphinx and the pyramids of Giza
Limestone is the common name for calcium carbonate, CaCO3. Just as you learned how to write chemical formulas for binary ionic compounds, you will now learn how to write formulas for ionic compounds that contain polyatomic ions.
Because these are ionic compounds, there still needs to be a balancing of charges to create a neutral substance. One of the key points to remember when writing formulas for ionic compounds that contain polyatomic ions is to use brackets around the polyatomic ion when there is the need of a subscript.
Because these are ionic compounds, there still needs to be a balancing of charges to create a neutral substance. One of the key points to remember when writing formulas for ionic compounds that contain polyatomic ions is to use brackets around the polyatomic ion when there is the need of a subscript.
Hint: If the compound name ends with “ate” or “ite,” then it contains a polyatomic. There are also some polyatomic ions that end in “ide.”
Examples
Each example has a video to go with it. To play the video, click on the play icon next to the example.
Identify the type of compound.
sodium—metal
chlorite—polyatomic
This is an ionic compound.
chlorite—polyatomic
This is an ionic compound.
Write the ion symbols.
«math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msup»«mi»Na«/mi»«mo»+«/mo»«/msup»«mo»§#160;«/mo»«mo»§#160;«/mo»«msubsup»«mi»ClO«/mi»«mn»2«/mn»«mo»-«/mo»«/msubsup»«/math»
Determine the lowest common multiple of the two charges.
The lowest common multiple between 1 and 1 is 1.
Determine the factor to multiple each ion by.
«math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mtable columnspacing=¨0px¨ columnalign=¨right center left¨»«mtr»«mtd»«msup»«mi»Na«/mi»«mo»+«/mo»«/msup»«mo»§#160;«/mo»«mo»§#215;«/mo»«mo»§#160;«/mo»«mn»1«/mn»«mo»§#160;«/mo»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mo»§#160;«/mo»«mn»1«/mn»«mo»+«/mo»«mo»§#160;«/mo»«/mtd»«/mtr»«mtr»«mtd»«msubsup»«mi»ClO«/mi»«mn»2«/mn»«mo»-«/mo»«/msubsup»«mo»§#160;«/mo»«mo»§#215;«/mo»«mo»§#160;«/mo»«mn»1«/mn»«mo»§#160;«/mo»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mo»§#160;«/mo»«mn»1«/mn»«mo»§#8211;«/mo»«/mtd»«/mtr»«/mtable»«/math»
This will create a neutral compound.
The ratio of Na+ to «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msubsup»«mi»ClO«/mi»«mn»2«/mn»«mo»-«/mo»«/msubsup»«/math» is 1:1.
This will create a neutral compound.
The ratio of Na+ to «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msubsup»«mi»ClO«/mi»«mn»2«/mn»«mo»-«/mo»«/msubsup»«/math» is 1:1.
Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/sodiarn5sj ;
Identify the type of compound.
magnesium—metal
hydroxide—polyatomic
This is an ionic compound.
hydroxide—polyatomic
This is an ionic compound.
Write the ion symbols.
«math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msup»«mi»Mg«/mi»«msup»«mn»2«/mn»«mo»+«/mo»«/msup»«/msup»«mo»§#160;«/mo»«msup»«mi»OH«/mi»«mo»§#8211;«/mo»«/msup»«/math»
Determine the lowest common multiple of the two charges.
The lowest common multiple between 2 and 1 is 2.
Determine the factor to multiple each ion by.
«math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mtable columnspacing=¨0px¨ columnalign=¨right center left¨»«mtr»«mtd»«msup»«mi»Mg«/mi»«msup»«mn»2«/mn»«mo»+«/mo»«/msup»«/msup»«mo»§#160;«/mo»«mo»§#215;«/mo»«mo»§#160;«/mo»«mn»1«/mn»«mo»§#160;«/mo»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mo»§#160;«/mo»«mn»2«/mn»«mo»+«/mo»«mo»§#160;«/mo»«/mtd»«/mtr»«mtr»«mtd»«msup»«mi»OH«/mi»«mo»§#8211;«/mo»«/msup»«mo»§#160;«/mo»«mo»§#215;«/mo»«mo»§#160;«/mo»«mn»2«/mn»«mo»§#160;«/mo»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mo»§#160;«/mo»«mn»2«/mn»«mo»§#8211;«/mo»«/mtd»«/mtr»«/mtable»«/math»
This will create a neutral compound.
The ratio of «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msup»«mi»Mg«/mi»«msup»«mn»2«/mn»«mo»+«/mo»«/msup»«/msup»«/math» to OH– is 1:2.
This will create a neutral compound.
The ratio of «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msup»«mi»Mg«/mi»«msup»«mn»2«/mn»«mo»+«/mo»«/msup»«/msup»«/math» to OH– is 1:2.
Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/7atovzgclg
Identify the composition of the compound.
ammonium—polyatomic
fluoride—non-metal
This is an ionic compound.
fluoride—non-metal
This is an ionic compound.
Write the ion symbols.
«math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msubsup»«mi»NH«/mi»«mn»4«/mn»«mo»+«/mo»«/msubsup»«mo»§#160;«/mo»«mo»§#160;«/mo»«msup»«mi mathvariant=¨normal¨»F«/mi»«mo»§#8211;«/mo»«/msup»«/math»
Determine the lowest common multiple of the two charges.
The lowest common multiple between 1 and 1 is 1.
Determine the factor to multiple each ion by.
«math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mtable columnspacing=¨0px¨ columnalign=¨right center left¨»«mtr»«mtd»«msubsup»«mi»NH«/mi»«mn»4«/mn»«mo»+«/mo»«/msubsup»«mo»§#160;«/mo»«mo»§#215;«/mo»«mo»§#160;«/mo»«mn»1«/mn»«mo»§#160;«/mo»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mo»§#160;«/mo»«mn»1«/mn»«mo»+«/mo»«/mtd»«/mtr»«mtr»«mtd»«msup»«mi mathvariant=¨normal¨»F«/mi»«mo»§#8211;«/mo»«/msup»«mo»§#160;«/mo»«mo»§#215;«/mo»«mo»§#160;«/mo»«mn»1«/mn»«mo»§#160;«/mo»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mo»§#160;«/mo»«mn»1«/mn»«mo»§#8211;«/mo»«/mtd»«/mtr»«/mtable»«/math»
This will create a neutral compound.
The ratio of «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msubsup»«mi»NH«/mi»«mn»4«/mn»«mo»+«/mo»«/msubsup»«/math» to F– is 1:1.
This will create a neutral compound.
The ratio of «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msubsup»«mi»NH«/mi»«mn»4«/mn»«mo»+«/mo»«/msubsup»«/math» to F– is 1:1.
Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/xkw64p8llr
Identify the type of compound.
aluminium—metal
sulfate—polyatomic
This is an ionic compound.
sulfate—polyatomic
This is an ionic compound.
Write the ion symbols.
«math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msup»«mi»Al«/mi»«msup»«mn»3«/mn»«mo»+«/mo»«/msup»«/msup»«mo»§#160;«/mo»«mo»§#160;«/mo»«msubsup»«mi»SO«/mi»«mn»4«/mn»«mrow»«mn»2«/mn»«mo»-«/mo»«/mrow»«/msubsup»«/math»
Determine the lowest common multiple of the two charges.
The lowest common multiple between 3 and 2 is 6.
Determine the factor to multiple each ion by.
«math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mtable columnspacing=¨0px¨ columnalign=¨right center left¨»«mtr»«mtd»«msup»«mi»Al«/mi»«msup»«mn»3«/mn»«mo»+«/mo»«/msup»«/msup»«mo»§#160;«/mo»«mo»§#215;«/mo»«mo»§#160;«/mo»«mn»2«/mn»«mo»§#160;«/mo»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mo»§#160;«/mo»«mn»6«/mn»«mo»+«/mo»«/mtd»«/mtr»«mtr»«mtd»«msubsup»«mi»SO«/mi»«mn»4«/mn»«mrow»«mn»2«/mn»«mo»-«/mo»«/mrow»«/msubsup»«mo»§#160;«/mo»«mo»§#215;«/mo»«mo»§#160;«/mo»«mn»3«/mn»«mo»§#160;«/mo»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mo»§#160;«/mo»«mn»6«/mn»«mo»§#8211;«/mo»«/mtd»«/mtr»«/mtable»«/math»
This will create a neutral compound.
The ratio of «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msup»«mi»Al«/mi»«msup»«mn»3«/mn»«mo»+«/mo»«/msup»«/msup»«/math» to «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msubsup»«mi»SO«/mi»«mn»4«/mn»«mrow»«mn»2«/mn»«mo»-«/mo»«/mrow»«/msubsup»«/math» is 2:3.
This will create a neutral compound.
The ratio of «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msup»«mi»Al«/mi»«msup»«mn»3«/mn»«mo»+«/mo»«/msup»«/msup»«/math» to «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msubsup»«mi»SO«/mi»«mn»4«/mn»«mrow»«mn»2«/mn»«mo»-«/mo»«/mrow»«/msubsup»«/math» is 2:3.
Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/00g9pxgtli
Identify the type of compound.
lithium—metal
hydrogen phosphate—polyatomic
This is an ionic compound.
hydrogen phosphate—polyatomic
This is an ionic compound.
Write the ion symbols.
«math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msup»«mi»Li«/mi»«mo»+«/mo»«/msup»«mo»§#160;«/mo»«mo»§#160;«/mo»«msubsup»«mi»HPO«/mi»«mn»4«/mn»«mrow»«mn»2«/mn»«mo»-«/mo»«/mrow»«/msubsup»«/math»
Determine the lowest common multiple of the two charges.
The lowest common multiple between 2 and 1 is 2.
Determine the factor to multiple each ion by.
«math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mtable columnspacing=¨0px¨ columnalign=¨right center left¨»«mtr»«mtd»«msup»«mi»Li«/mi»«mo»+«/mo»«/msup»«mo»§#160;«/mo»«mo»§#215;«/mo»«mo»§#160;«/mo»«mn»2«/mn»«mo»§#160;«/mo»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mo»§#160;«/mo»«mn»2«/mn»«mo»+«/mo»«/mtd»«/mtr»«mtr»«mtd»«msubsup»«mi»HPO«/mi»«mn»4«/mn»«mrow»«mn»2«/mn»«mo»-«/mo»«/mrow»«/msubsup»«mo»§#160;«/mo»«mo»§#215;«/mo»«mo»§#160;«/mo»«mn»1«/mn»«mo»§#160;«/mo»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mo»§#160;«/mo»«mn»2«/mn»«mo»§#8211;«/mo»«/mtd»«/mtr»«/mtable»«/math»
This will create a neutral compound.
The ratio of Li+ to «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msubsup»«mi»HPO«/mi»«mn»4«/mn»«mrow»«mn»2«/mn»«mo»-«/mo»«/mrow»«/msubsup»«/math» is 2:1.
This will create a neutral compound.
The ratio of Li+ to «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msubsup»«mi»HPO«/mi»«mn»4«/mn»«mrow»«mn»2«/mn»«mo»-«/mo»«/mrow»«/msubsup»«/math» is 2:1.
Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/h941wfwzfh
Read This
Please read pages 44 to 46 in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on the rules for writing formulas
for ionic compounds that contain polyatomic ions. Remember, if you have any questions or you do not understand something, ask your teacher!
Practice Questions
Complete the following practice questions to check your understanding of the concept you just learned. Make sure you write complete answers to the practice questions in your notes. After you have checked your answers, make corrections to your responses
(where necessary) to study from.- Provide the correct IUPAC name for each of the following compounds.
zinc sulfate potassium dichromate ammonium iodide barium phosphate aluminium sulfite magnesium cyanide sodium hydrogen sulfide
zinc sulfate ZnSO4 potassium dichromate K2Cr2O7 ammonium iodide NH4I barium phosphate BA3(PO4)2 aluminium sulfite Al2(SO3)3 magnesium cyanide Mg(CN)2 sodium hydrogen sulfide NaHS