Lesson 5 Ionic Compounds - Naming and Formulas
Completion requirements
Naming Ionic Compounds that Contain Multivalent Ions
Can you believe that these two containers both hold copper chloride?
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B5.11 White solid in a liquid
B5.11 White solid in a liquid
When naming ionic compounds that contain multivalent ions, the valency (charge) of the transition metal must be identified as a Roman numeral written directly after the metal name. The vial in image B5.11 contains copper(I) chloride, a white solid with
low solubility in water; and the vial in image B5.12 contains a solution of copper(II) chloride, which is highly soluble in water.
Eighty percent of the time if you uncross the subscripts (from the swap and drop), the correct charge on the multivalent ion is indicated. The exception would be when charges were reduced; so remember to also check the charge on the anion.
Eighty percent of the time if you uncross the subscripts (from the swap and drop), the correct charge on the multivalent ion is indicated. The exception would be when charges were reduced; so remember to also check the charge on the anion.
It should be noted that according to IUPAC nomenclature standards, no space is placed between the name of the multivalent cation and the bracketed Roman numeral. For example, it is incorrect to name CuCl as copper (I) chloride. Rather,
it should be named copper(I) chloride. Please notice this important detail as you work through the following examples to solidify your understanding of multivalent ionic nomenclature.
B5.12 Blue liquid in a vial
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 composition of the compound.
Co—multivalent metal
Cl—non-metal
This is an ionic compound that needs Roman numerals.
Cl—non-metal
This is an ionic compound that needs Roman numerals.
Write the name of the cation.
cobalt
Cobalt is multivalent, so it will either be cobalt(II) or cobalt(III).
“Uncross” the subscripts to determine the charge on cobalt.
As a double check, look on the periodic table: Is the charge on chloride 1–? Yes! This means that the formula has not been reduced and this method is valid.
Cobalt is multivalent, so it will either be cobalt(II) or cobalt(III).
“Uncross” the subscripts to determine the charge on cobalt.
As a double check, look on the periodic table: Is the charge on chloride 1–? Yes! This means that the formula has not been reduced and this method is valid.
Write the name of the anion (if it is a polyatomic, do not change the ending; if it is a non-metallic element, change the ending to “ide”).
Cl is the non-metal chlorine, so the end changes to “ide.”
chloride
chloride
Combine the ion names, including the Roman numeral representing the charge on the cation.
cobalt(II) chloride
Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/2px35op6kq
Identify the composition of the compound.
Fe—multivalent metal
S—non-metal
This is an ionic compound that needs Roman numerals.
S—non-metal
This is an ionic compound that needs Roman numerals.
Write the name of the cation.
iron
Iron is multivalent, so it will either be iron(II) or iron(III).
“Uncross” the subscripts to determine the charge on iron.
As a double check, look on the periodic table: Is the charge on sulfide 2-? Yes! This means that the formula has not been reduced and this method is valid.
Iron is multivalent, so it will either be iron(II) or iron(III).
“Uncross” the subscripts to determine the charge on iron.
As a double check, look on the periodic table: Is the charge on sulfide 2-? Yes! This means that the formula has not been reduced and this method is valid.
Write the name of the anion (if it is a polyatomic, do not change the ending; if it is a non-metallic element, change the ending to “ide”).
S is the non-metal sulfur, so the end changes to “ide.”
sulfide
sulfide
Combine the ion names, including the Roman numeral representing the charge on the cation.
iron(III) sulfide
Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/c0odxvlpcc
Identify the composition of the compound.
Sn—multivalent metal
O—non-metal
This is an ionic compound that needs Roman numerals.
O—non-metal
This is an ionic compound that needs Roman numerals.
Write the name of the cation.
tin
Tin is multivalent, so it will either be tin(II) or tin(IV).
“Uncross” the subscripts to determine the charge on tin.
As a double check, look on the periodic table: Is the charge on oxide 1–? No! This means that the formula has been reduced, the charge on oxide is 2–, so this compound has been reduced by a factor of 2; therefore the charge on Sn needs to be doubled—«math»«msup»«mi»Sn«/mi»«msup»«mn»4«/mn»«mo»+«/mo»«/msup»«/msup»«/math».
Tin is multivalent, so it will either be tin(II) or tin(IV).
“Uncross” the subscripts to determine the charge on tin.
As a double check, look on the periodic table: Is the charge on oxide 1–? No! This means that the formula has been reduced, the charge on oxide is 2–, so this compound has been reduced by a factor of 2; therefore the charge on Sn needs to be doubled—«math»«msup»«mi»Sn«/mi»«msup»«mn»4«/mn»«mo»+«/mo»«/msup»«/msup»«/math».
Write the name of the anion (if it is a polyatomic, do not change the ending; if it is a non-metallic element, change the ending to “ide”).
O is the non-metal oxygen, so the end changes to “ide.”
oxide
oxide
Combine the ion names, including the Roman numeral representing the charge on the cation.
tin(IV) oxide
Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/xp3pxkknks
Identify the composition of the compound.
Cr—multivalent metal
«math»«msubsup»«mi»NO«/mi»«mn»3«/mn»«mo»-«/mo»«/msubsup»«/math»—polyatomic
This is an ionic compound that needs Roman numerals.
«math»«msubsup»«mi»NO«/mi»«mn»3«/mn»«mo»-«/mo»«/msubsup»«/math»—polyatomic
This is an ionic compound that needs Roman numerals.
Write the name of the cation.
chromium
Chromium is multivalent, so it will either be chromium(II) or chromium(III).
“Uncross” the subscripts to determine the charge on tin.
As a double check, look on the table of polyatomics: Is the charge on NO3 1–? Yes! This means that the formula has not been reduced and this method is valid.
Chromium is multivalent, so it will either be chromium(II) or chromium(III).
“Uncross” the subscripts to determine the charge on tin.
As a double check, look on the table of polyatomics: Is the charge on NO3 1–? Yes! This means that the formula has not been reduced and this method is valid.
Write the name of the anion (if it is a polyatomic, do not change the ending; if it is a non-metallic element, change the ending to “ide”).
«math»«msubsup»«mi»NO«/mi»«mn»3«/mn»«mo»-«/mo»«/msubsup»«/math» is a polyatomic.
nitrate
nitrate
Combine the ion names, including the Roman numeral representing the charge on the cation.
chromium(III) nitrate
Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/zqjej3g4eu
Read This
Please read page 44 in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on how to determine the charge on the
multivalent ion in an ionic compound. 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.
CrBr3 HgS Ni2O3 MnO2 Fe3(Po4)2
CrBr3 chromium(III) bromide HgS mercury(II) sulfide Ni2O3 nickel(III) oxide MnO2 manganese(IV) oxide Fe3(Po4)2 iron(II) phosphate