How to do Ionic Formulas to Names
This set of instructions will take in the reverse path of names to formulas. I
believe that once a student understands one direction the instruction to go
the other way is easier. However, we will walk through with more detail
than is needed in the event you are starting with this method first. You will
need you periodic table to perform this activity.
These practice problems are for your use. I encourage you to use all of the
steps outlined until you feel very comfortable in the process. An “ide”
ending means there are only two different atoms present in the compound.
The “ide” ending will modify the name of the compound so you need to
change the name for an element so that it sound familiar, it is OK to guess
at this part as there are not rules to follow.
Convert MgCl2 to a name
1. Look at the back of the periodic table. In the upper right corner is a
box with the name formula to name. The first question is “Is the
compound ionic? “
2. The answer is yes it is made of a metal and non-metal.
3. Next question is does the cation (the first element in the formula)
have more than one oxidation number.
4. Look on the front of the periodic table and you will see that
magnesium is in the second column on the left and they all have only
one number and that is a 2.
5. Now you write the full name of the cation and if there are only two
different atoms present, write the anion with an ending of “ide”.
Convert Fe2O3 to a name
1. Again, the first question is the compound ionic.
2. The answer is yes, as it is made up of a metal and non-metal.
3. This flows you over to the left side and the next question is does the
cation have more than one oxidation number.
4. The answer is yes. Iron has two numbers 2 and 3.
5. We do not know from the formula which one is used, so we have to do
a bit of math to determine the oxidation number.
6. At the bottom of the periodic table, back is a box labeled how to
determine an oxidation number. You can see that it is the same
7. Oxygen nearly always is a -2-oxidation number. Therefore, you can
use this number multiplied by the number of oxygen present which is
three (3) in number so the total negative charge is -6. All formulas
unless otherwise indicated have a neutral or zero charge overall.
8. Therefore, this means that the iron brings a +6 to the formula.
9. As there are 2 iron atoms that means that each atom has a charge of
10. Therefore you write the name of the cation with its oxidation
number as a Roman numeral and follow it with the anion.
11. there are only two atoms present so it is a binary compound with
an “ide” ending
Iron III oxide
Convert BaCO3 to a name
1. You ask is the compound ionic and yes it is.
2. Does the cation have more than one oxidation state?
3. You notice that it is in the second column on the left and all of these
atoms have a +2 charge.
4. Now you notice that the name does not end in “ide” so you need to look
on the back of the periodic table on the left side under the box labeled
5. You will find the most common ones, but this is not an exhaustive list.
6. Carbonate has the same formula and its charge is a -2.
7. so the cation is written first with the full name of the polyatomic anion
Convert Ni(NO3)2 to a name
1. This is the last of the bunch.
2. Look to see if it is an ionic compound.
3. It is ionic and you note that the name does not end in “ide”.
4. By now, you realize that you are dealing with a polyatomic ion, but you
are not sure of the cation.
5. You look up Ni and you find that it is nickel and it has several oxidation
6. So just like the iron III oxide, you will need to do some math to
determine which of the oxidation states you need to use.
7. You find the polyatomic ion on the back and you note that nitrate has a -
8. The formula indicates that there are two nitrates present and that there
is only one nickel present.
9. this makes it easier as the negative 2 must be balanced with w positive 2
and because there is only one nickel atom present the charge on nickel is
10. The name of the cation is written in full with the charge written as a
Roman numeral and this is followed by the polyatomic anion with its
name in full.
Nickel II nitrate