We’ll go over another example of naming an ionic compound that has a polyatomic ion in its...

We’ll go over another example of naming an ionic compound that has a polyatomic ion in its formula.

Naming Compounds with Polyatomic Ions

Example 3

We’re asked to name the compound with the formula Sn, Cr2O7 in brackets, 2.

Name the compound with the formula Sn(Cr2O7)2

We see that Sn(Cr2O7)2 has 3 elements (click) tin, chromium, and oxygen. Any ionic compound with more than two elements must contain a polyatomic ion.

Sn(Cr2O7)2

3 Elements


So we look for polyatomic ions in the formula Sn(Cr2O7)2


Sn(Cr2O7)

2

We see that Cr2O7 with a negative 2 charge is called dichromate

Sn(Cr2O7)

2


And the metal Sn is found (click) on positive ion section of this table.

Sn(Cr2O7)

2


We see that Sn is tin and it is a multivalent metal. It can have a charge of either positive 2 or positive 4.

Sn(Cr2O7)

2


This is verified by finding tin on the periodic table, we see, it has these two different possible charges

Sn(Cr2O7)

2


The formula tell us we have one Sn ion


Sn4+ Cr2O72–

+4 –4Cr2O7

2–

And 2 Cr2O7 ions.


Sn4+ Cr2O72–

+4 –4Cr2O7

2–

The ion table tells us the Cr2O7 is called dichromate,


Sn4+ Cr2O72–

+4 –4Cr2O7

2–

So we can start the name by writing (click) tin dichromate


Sn4+ Cr2O72–

+4 –4Cr2O7

2–

tin(IV) dichromate

Tin is a multivalent metal with a charge of either positive 4 or positive 2, so we need a roman numeral (click) after tin in the name


Sn4+ Cr2O72–

+4 –4Cr2O7

2–

tin(IV) dichromate

?

We don’t know what roman numeral to use at this point. We determine that by finding the charge the tin ion needs to have to balance the total negative charge on the dichromate ions


Sn4+ Cr2O72–

+4 –4Cr2O7

2–

tin(IV) dichromate?

The ion table tells us that (click) each dichromate ion has a charge of negative 2


Sn4+ Cr2O72–

+4 –4Cr2O7

2–

tin(IV) dichromate

So the total negative charge is negative 2 plus negative 2 (click) which is negative 4


Sn4+ Cr2O72–

+4 –4Total Positive Charge

Total Negative Charge

Cr2O72–

tin(IV) dichromate

The charges must be balanced, (click) so the total positive charge is positive 4


Sn4+ Cr2O72–



Cr2O72–

tin(IV) dichromate

The total positive charge is positive 4 and there is only one tin ion, (click) so the charge on one tin ion must be positive 4


Sn4+ Cr2O72–



Cr2O72–

tin(IV) dichromate

Therefore, the roman numeral we use is (click) “I” “V” for 4


Sn4+ Cr2O72–



Cr2O72–

tin(IV) dichromate

So the final name is tin four dichromate.


Sn4+ Cr2O72–



Cr2O72–

tin(IV) dichromate Name

So the final answer to the question is is, the name of this compound (click) is tin four dichromate.


tin(IV) dichromate

We’ll go over another example of naming an ionic compound that has a polyatomic ion in its...

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