Ionic compounds are a type of chemical compound composed of metal cations (positive ions) and non-metallic anions (negative ions). To name an ionic compound, all you need to do is look up the names of the cations and anions that make up the compound and make sure to change the ending of the metal name as needed. First, write the name of the metal, followed by the name of the nonmetal with the new ending. For problems with ionic compounds with transition metals, also calculate the charge on the metal ion as an additional step.
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Method 1 of 3: Naming the Basic Ionic Compound
Step 1. Look at the periodic table of the elements
To name an ionic compound, all the information you need is actually in the periodic table. Ionic compounds are formed from metal ions (cations) and nonmetals (anions). You can look for metallic elements on the left and center of the periodic table (for example, Barium, Radium, and Lead), and look for non-metallic elements on the right side of the periodic table.
- Anions generally belong to groups 15, 16, or 17 on the periodic table. Most versions of the periodic table use color coding to identify metallic and nonmetallic elements.
- If you don't have a copy of the periodic table, you can view it online at:
Step 2. Write the formula for the ionic compound
Assume that the ionic compound in your problem is NaCl. Use a pen or pencil to write the formula for this compound on paper. Or, in the classroom, write "NaCl" on the board.
This is an example of a basic ionic compound. Basic ionic compounds do not have transition metals and are composed of only 2 ions
Step 3. Write down the metal name
The first part of the ionic compound is called the "cation" which is a metal. This is the positively charged part of the compound and is always written first in the formula for the ionic compound. Look at the periodic table for the element name "Na" if necessary. "Na" is sodium. So, write "sodium."
Whatever the ionic compound in the problem, the name of the metal is always written first
Step 4. Add the suffix "ide" to the nonmetal ion
The second component in ionic compounds is the nonmetal anion. Write the name of this non-metallic component along with the suffix "ida". As per the example above, the anion component is "Cl", i.e. chlorine. To add the "ida" ending, simply subtract 1-2 syllables (in this case -in) from the nonmetal name and replace it with "ida". That way, "Chlorine" will become "Chloride".
This naming rule also applies to other anions. For example, in an ionic compound, "Phosphorus" would become "Phosphide" and "Iodine" would become "Iodide"
Step 5. Combine the names of the cations and anions
After finding names for the two components of an ionic compound, you're almost done! Now you just need to combine them. So, "NaCl" can be written as "sodium chloride".
Step 6. Practice naming simpler ionic compounds
Now that you know how to name ionic compounds, try naming some of the simpler ionic compounds. Remembering some commonly found ionic compounds can help you better understand how to name ionic compounds. Remember that you don't need to pay attention to the number of ions separately when naming compounds. The following are some examples of commonly found ionic compounds:
- Li2S = Lithium sulfide
- Ag2S = Silver sulfide
- MgCl2 = magnesium chloride
Method 2 of 3: Naming Ionic Compounds That Have Transition Metals
Step 1. Write the formula for the ionic compound
For example, suppose you are working on the following compound problem: Fe2O3. Transition metals can be found in the middle of the periodic table, among them, Platinum, Gold, and Zirconium. You must include Roman numerals in the name of an ionic compound like this.
Transition metals need more attention in naming ionic compounds because their oxidation number (or charge) can change
Step 2. Find out the metal charge
If the metal ions in your compound are from group 3 (or more) on the periodic table, you'll need to find out their charge first. The subscript number under the metal-pair anion indicates the charge of the transition metal. Metals have a positive charge. So, in this example problem, cross the number 3 of O3 and write the +3 charge on Fe.
- You can also do the opposite and write a charge of -2 on the O.
- The charge of metal ions is usually listed in chemistry exam questions at the high school or university level.
Step 3. Write the name of the metal and include roman numerals as needed
Read the periodic table if you need to find out the chemical code for the metal in the problem. Since the "Fe" in the problem is iron with a +3 charge, you can write Iron(III).
Remember to only use roman numerals when writing the name of an ionic compound, and not when writing the chemical formula
Step 4. Write the name of the nonmetal by changing the ending
Read the periodic table if you forget the name of the anion. Since "O" is oxygen, you can remove the "-gene" ending and replace it with "-ide" to make "oxide".
Anions always use the -ide ending. So, the name of the anion will always be the same regardless of the metal pair in the ionic compound
Step 5. Combine the names of the cations and anions to form the name of the ionic compound
This part is exactly the same as writing the name of an ionic compound that does not have a transition metal. Simply combine the names of metals (along with their roman numerals) and nonmetals to form the name of the ionic compound: Fe2O3 = Iron (III) oxide.
Step 6. Use the old naming method instead of roman numerals
In the old naming method, transition metal names had the endings "o" and "i". Consider the two components in the compound. If the metallic charge is lower than the nonmetal, use the "o" suffix, while otherwise the metallic charge is higher, use the "i" suffix.
- Fe2+ has a lower charge than oxygen (Fe3+ has a higher charge) so that "Fe" becomes ferrous. Thus the Fe. compound2+O can also be written as ferrous oxide.
- The terms "ferry" and "ferrous" are used to refer to ferrous ions because the symbol for iron is "Fe".
Step 7. Do not use roman numerals when naming compounds containing zinc or silver
Two transition metals that have a fixed charge are zinc (Zn) and silver (Ag). Thus, metal charges in ionic compounds composed of zinc or silver do not assign subscript numbers to the anions. Zinc is always +2 and silver is always +1.
This means, you don't need to add roman numerals or use old naming methods to name the two elements
Method 3 of 3: Naming Ionic Compounds with Polyatomic Ions
Step 1. Write the formula for the polyatomic ion
Polyatomic ionic compounds have more than 2 ions. In most polyatomic compounds, one of the ions is a metal and the rest is a nonmetal. As always, read the periodic table for the name of each ion. Suppose you are working on the following compound problem: FeNH4(SO4)2.
Step 2. Find out the charge of the metal ion
First SO. ions4 has a charge of -2. You can also tell that there are 2 of these ions in the compound by writing the number 2 under the brackets. This ion is called "sulfate" because it is a combination of oxygen and sulfur. So, the charge is 2 x -2 = -4. Next, NH4, or the ammonium ion has a +1 charge. You can tell that this ion is positively charged because ammonia itself is neutral, while ammonium has 1 extra hydrogen molecule. (Ammonium is so called because it combines 1 molecule of nitrogen and 4 molecules of hydrogen.) Add -4 and 1, so the result is -3. This means that the iron ion, Fe, must have a +3 charge to make this compound neutral.
- Ionic compounds are always neutrally charged. You can use this information to calculate the charge of a metal ion.
- SO4 It has a -2 charge because it lacks the 2 hydrogen atoms present if it is in the form of sulfuric acid.
Step 3. Name the metal ion
You can name metal ions differently depending on whether you're using the old or new naming method. So, to name a metal ion, you can write Iron(III) or ferric.
Step 4. Write down the nonmetal ion
Read the periodic table to find out that "S" is sulfur. Ammonium is not an element, but it is formed when 1 nitrogen ion bonds with 4 hydrogen ions. So you need to write "ammonium" and "sulfate", or "ammonium sulfate".
"Ammonia" will become "ammonium" if it is positively charged. Ammonia itself is neutral
Step 5. Combine the names of metal and nonmetal ions
In this example, write the name of the compound FeNH4(SO4)2 as Iron(III) ammonium sulfate.
