Naming Binary Compounds
There are certain elements, cations, and anions that you MUST know before you get started. Position in the periodic table can help you remember many, but not all. For any name you should be able to write the formula and for any formula you should be able to write the name including spelling.
You should know the first 38 elements and Au, U, Ag, Sn, Hg, Cd, Sb, I, Xe, Cs, Ba, Rn, Ra, and Pb
Compounds with common names:
Cations
Names Symbols
Common Monatomic Anions
Name Symbol Name Symbol Name Symbol
Hydride H- Iodide I- Telluride Te2-
Fluoride F- Oxide O2- Nitride N3-
Chloride Cl- Sulfide S2- Phosphide P3-
Bromide Br- Selinide Se2- Arsenide As3-
Common Polyatomic Anions (two or more atoms)
Name Formula Name Formula Name Formula
Nitrate NO3- Sulfate SO42- Nitrite NO2-
Permanganate MnO4- Carbonate CO32- Dichromate Cr2O72-
Hydroxide OH- Chromate CrO42- Sulfite SO32-
Cyanide CN- Phosphate PO43- Chlorite ClO2-
Perchlorate ClO4- Peroxide O22- Hypochlorite ClO-
Thiocyanate SCN- Chlorate ClO3- Acetate C2H3O2-
Bicarbonate HCO3- Bisulfate HSO4- Arsenate AsO43-
Oxalate C2O42- Bromate BrO3-
Acids
Sulfuric H2SO4 Perchloric HClO4 Hydrocyanic HCN
Phosphoric H3PO4 Chloric HClO3 Chlorous HClO2
Nitric HNO3 Hydrobromic HBr Hypochlorous HClO
Hydrochloric HCl Hydroiodic HI Nitrous HNO2
Bases
Lithium hydroxide LiOH Magnesium hydroxide Mg(OH)2
Sodium hydroxide NaOH Calcium hydroxide Ca(OH)2
Potassium hydroxide KOH Strontium hydroxide Sr(OH)2
Cesium hydroxide CsOH
Rubidium hydroxide RbOH
There are four main classes of inorganic compounds we will learn how to name:
1. Compounds made from single valence metals.
2. Compounds made from multivalent metals.
3. Compounds containing only nonmetallic elements.
4. Acids.
You should know the first 38 elements and Au, U, Ag, Sn, Hg, Cd, Sb, I, Xe, Cs, Ba, Rn, Ra, and Pb
Compounds with common names:
- H2O - water
- H2O2 - hydrogen peroxide
- NH3 - ammonia
Cations
Names Symbols
- Lithium ion, sodium ion, etc. Li+, Na+, K+, Rb+, Cs+
- Beryllium ion, magnesium ion, etc. Be2+, Mg2+, Ca2+, Sr2+, Ba2+
- Hydronium ion H+
- Aluminum ion Al3+
- Iron(II), Iron(III) Fe2+, Fe3+
- Copper(I), Copper(II) Cu+, Cu2+
- Silver ion Ag+
- Mercury(I), Mercury(II) Hg22+, Hg2+
- Lead(II), Lead(IV) Pb2+, Pb4+
- Ammonium ion NH4+
- Cadmium ion Cd2+
- Zinc ion Zn2+
- Nickel(II), Nickel(IV) Ni2+, Ni4+
- Gold(I), Gold(IV) Au+, Au4+
- Cobalt(II), Cobalt(III) Co2+, Co3+
- Tin(II), Tin(IV) Sn2+, Sn4+
- Chromium(II), Chromium(III) Cr2+, Cr3+
Common Monatomic Anions
Name Symbol Name Symbol Name Symbol
Hydride H- Iodide I- Telluride Te2-
Fluoride F- Oxide O2- Nitride N3-
Chloride Cl- Sulfide S2- Phosphide P3-
Bromide Br- Selinide Se2- Arsenide As3-
Common Polyatomic Anions (two or more atoms)
Name Formula Name Formula Name Formula
Nitrate NO3- Sulfate SO42- Nitrite NO2-
Permanganate MnO4- Carbonate CO32- Dichromate Cr2O72-
Hydroxide OH- Chromate CrO42- Sulfite SO32-
Cyanide CN- Phosphate PO43- Chlorite ClO2-
Perchlorate ClO4- Peroxide O22- Hypochlorite ClO-
Thiocyanate SCN- Chlorate ClO3- Acetate C2H3O2-
Bicarbonate HCO3- Bisulfate HSO4- Arsenate AsO43-
Oxalate C2O42- Bromate BrO3-
Acids
Sulfuric H2SO4 Perchloric HClO4 Hydrocyanic HCN
Phosphoric H3PO4 Chloric HClO3 Chlorous HClO2
Nitric HNO3 Hydrobromic HBr Hypochlorous HClO
Hydrochloric HCl Hydroiodic HI Nitrous HNO2
Bases
Lithium hydroxide LiOH Magnesium hydroxide Mg(OH)2
Sodium hydroxide NaOH Calcium hydroxide Ca(OH)2
Potassium hydroxide KOH Strontium hydroxide Sr(OH)2
Cesium hydroxide CsOH
Rubidium hydroxide RbOH
There are four main classes of inorganic compounds we will learn how to name:
1. Compounds made from single valence metals.
2. Compounds made from multivalent metals.
3. Compounds containing only nonmetallic elements.
4. Acids.
Compounds Made From Single Valence Metals
In general, these compounds are made using at least one of the metals in Groups IA, IIA, and IIIA. These metals donate electrons readily (they have a low ionization energy) and always have oxidation numbers corresponding to their group number. For example, K, Na, Cs, etc., have oxidation numbers of +1 only. All we have to do is specify the cation (the ionic metal) followed by the anion. We must also ensure that the sum of the oxidation numbers is zero (for we are dealing with neutral molecules). Here are some examples:
NaH sodium hydride
Cs2O cesium oxide
BaF2 barium fluoride
HCN hydrogen cyanide (cyanic acid)
Sr3N2 strontium nitride
Ca(OH)2 calcium hydroxide
Li3PO4 lithium phosphate
MgSO4 magnesium sulfate
Now, you try a couple:
a. Na2CrO4 __________________________
b. magnesium fluoride ___________________________
In question (a), the cation is Na+ (sodium) and the anion is CrO42- (chromate). Thus, the compound is sodium chromate. In question (b), magnesium exists in compound form as Mg2+. Fluoride is the F- anion. To make the compound neutral, we need two F-‘s. Therefore, the formula for magnesium fluoride is MgF2.
If we have an ionic compound that contains hydrogen along with the cation, then we need to specify the number of hydrogen atoms in the compound. For instance,
NaHCO3 sodium hydrogen carbonate or sodium bicarbonate
Na2HPO4 sodium monohydrogen phosphate
NaH2PO4 sodium dihydrogen phosphate
In the above examples, we use Greek prefix before the word “hydrogen” to specify the number of hydrogens. In case you’ve forgotten, here are the prefixes:
Note:
Notice that for NaHCO3, the number of hydrogens is not specified. This is because carbonate has a –2 charge; if sodium (Na+) combines with CO32-, there is only “room” for one hydrogen. Thus, the mono- is inferred in this case.
NaH sodium hydride
Cs2O cesium oxide
BaF2 barium fluoride
HCN hydrogen cyanide (cyanic acid)
Sr3N2 strontium nitride
Ca(OH)2 calcium hydroxide
Li3PO4 lithium phosphate
MgSO4 magnesium sulfate
Now, you try a couple:
a. Na2CrO4 __________________________
b. magnesium fluoride ___________________________
In question (a), the cation is Na+ (sodium) and the anion is CrO42- (chromate). Thus, the compound is sodium chromate. In question (b), magnesium exists in compound form as Mg2+. Fluoride is the F- anion. To make the compound neutral, we need two F-‘s. Therefore, the formula for magnesium fluoride is MgF2.
If we have an ionic compound that contains hydrogen along with the cation, then we need to specify the number of hydrogen atoms in the compound. For instance,
NaHCO3 sodium hydrogen carbonate or sodium bicarbonate
Na2HPO4 sodium monohydrogen phosphate
NaH2PO4 sodium dihydrogen phosphate
In the above examples, we use Greek prefix before the word “hydrogen” to specify the number of hydrogens. In case you’ve forgotten, here are the prefixes:
- mono � 1
- di � 2
- tri � 3
- tetra � 4
- penta � 5
- hexa � 6
- hepta � 7
- octa � 8
Note:
- The prefix mono is never used for naming the first element of a compound.
- The final "o" or "a" of a prefix is often dropped when the element begins with a vowel.
Notice that for NaHCO3, the number of hydrogens is not specified. This is because carbonate has a –2 charge; if sodium (Na+) combines with CO32-, there is only “room” for one hydrogen. Thus, the mono- is inferred in this case.
Compounds Made From Multivalent Metals (Stock System)
Nonionic metals can usually have more than one oxidation state. Iron, for instance, can be found as Fe3+ and as Fe2+. Most other transition metals can also assume more than one oxidation state. The way we distinguish between compounds which differ in oxidation numbers is by using Roman numerals, which is known as the Stock system. The Roman numeral indicates the oxidation number of the cation and is enclosed in parentheses immediately after the metal name. Take a look at these examples: FeSO4 iron(II) sulfate Fe2(SO4)3 iron(III) sulfate
PbO2 lead(IV) oxide
Sn(NO3)2 tin(II) nitrate
CuCN copper(I) cyanide
Hg(OH)2 mercury(II) hydroxide
Note the sum of the oxidation number(s) of the metal exactly cancels the sum of the negative charge(s) of the anion. Note also that you need not memorize the oxidation number of the metal because you can always back calculate its value by knowing the charge on the anion. In other words, MEMORIZE the anions, both name and charge.
Let’s try a couple:
a. CuSO4 ___________________________
b. iron(III) carbonate __________________________
In (a), remember to key off the anion! Since you’ve already memorized (?) the anions, you know that sulfate has a –2 charge. To make the compound neutral, you know that copper must have a +2 charge. Since copper is multivalent, we will express its oxidation state when we name the compound: copper(II) sulfate. For (b), the (III) tells us that the iron is in the +3 state (Fe3+). We know from our memorized list of anions that carbonate has a –2 charge (CO32-). To make a neutral iron(III) carbonate formula, we must balance the negative and positive charge. Two Fe3+’s and three CO32-‘s would balance the charge at +6 and –6: Fe2(CO3)3.
As with most topics in chemistry, there are always some exceptions. A number of metals exist which are not in Groups I or II and have one oxidation state. For these compounds, you do not specify the oxidation state in parenthesis. The exceptions you should know are Ag(+1), Cd(+2), Zn(+2), and Al(+3). Here are some examples of what we’re talking about:
AgMnO4 silver permanganate
CdCl2 cadmium chloride
AlH3 aluminum hydride
Zn(OH)2 zinc hydroxide
Remember, we used no Roman numerals in naming these exceptions. Note also that most transition metals can exhibit a +2 ion due to ionization of the 2s electrons.
PbO2 lead(IV) oxide
Sn(NO3)2 tin(II) nitrate
CuCN copper(I) cyanide
Hg(OH)2 mercury(II) hydroxide
Note the sum of the oxidation number(s) of the metal exactly cancels the sum of the negative charge(s) of the anion. Note also that you need not memorize the oxidation number of the metal because you can always back calculate its value by knowing the charge on the anion. In other words, MEMORIZE the anions, both name and charge.
Let’s try a couple:
a. CuSO4 ___________________________
b. iron(III) carbonate __________________________
In (a), remember to key off the anion! Since you’ve already memorized (?) the anions, you know that sulfate has a –2 charge. To make the compound neutral, you know that copper must have a +2 charge. Since copper is multivalent, we will express its oxidation state when we name the compound: copper(II) sulfate. For (b), the (III) tells us that the iron is in the +3 state (Fe3+). We know from our memorized list of anions that carbonate has a –2 charge (CO32-). To make a neutral iron(III) carbonate formula, we must balance the negative and positive charge. Two Fe3+’s and three CO32-‘s would balance the charge at +6 and –6: Fe2(CO3)3.
As with most topics in chemistry, there are always some exceptions. A number of metals exist which are not in Groups I or II and have one oxidation state. For these compounds, you do not specify the oxidation state in parenthesis. The exceptions you should know are Ag(+1), Cd(+2), Zn(+2), and Al(+3). Here are some examples of what we’re talking about:
AgMnO4 silver permanganate
CdCl2 cadmium chloride
AlH3 aluminum hydride
Zn(OH)2 zinc hydroxide
Remember, we used no Roman numerals in naming these exceptions. Note also that most transition metals can exhibit a +2 ion due to ionization of the 2s electrons.
Compounds Containing Only Nonmetallic Elements
Let’s move to the opposite end of the periodic table. Here we find the nonmetallic elements which are defined as having a high (negative) electron affinity. In general, the nonmetallic elements include those elements to the right and above the dark, solid stair-step line on the periodic table that forms a diagonal from boron (B) to astatine (At). Compounds formed solely from these elements will be covanlent in nature. When naming these molecules, we use Greek prefixes because the oxidation number for each element is not always obvious. The compound name begins with the most electropositive atom (the least electronegative) and then the other element is named (once again with the “ide” ending as in the anion). Let’s look at some examples:
CBr4 carbon tetrabromide
PF3 phosphorus trifluoride
N2O5 dinitrogen pentoxide
XeF6 xenon hexafluoride
Here are a couple for you to try!
a. NO _________________________
b. sulfur hexafluoride ____________________________
The formula in (a) is nitrogen monoxide. If there is only one of the more electropositive atoms, the “mono-“ prefix can be dropped. The “mono-“ prefix is always used for the more electronegative atom. In (b), no prefix on the sulfur implies one sulfur. Hexafluoride means six F-‘s. Therefore, the formula is SF6.
ACIDS
As a final note, we should talk about naming acids. You should be familiar with some common names, such as the following:
H2SO4 sulfuric acid
H3PO4 phosphoric acid
Most acids used in the laboratory can be classified as either binary or oxyacids (acids containing hydrogen, oxygen and a third element). All acids are named after the name of the anion. Three general rules apply:
- If the anion ends in –ide, then the acid is named hydro anion name-ic acid
- If the anion ends in –ate, then the acid is named anion name-ic acid
- If the anion ends in –ite, then the acid is named anion name-ous acid
For example,
HCl hydrochloric acid (from chloride)
HBr hydrobromic acid (from bromide)
HClO4 perchloric acid (from perchlorate ion)
HClO2 chlorous acid (from chlorite ion)
H2CrO4 chromic acid (from chromate ion)
HNO2 nitrous acid (from nitrite ion)
Most of the time, we will add the abbreviation for aqueous (aq) after the compound to indicate that it is dissolved in water and is, therefore, an acid. For instance, HI(aq) would be called hydroiodic aicd where as HI would be termed hydrogen iodide.
Nomenclature is an important part of the language of chemistry. Get used to naming these compounds. You’ll be seeing much more of them throughout the year!!!
CBr4 carbon tetrabromide
PF3 phosphorus trifluoride
N2O5 dinitrogen pentoxide
XeF6 xenon hexafluoride
Here are a couple for you to try!
a. NO _________________________
b. sulfur hexafluoride ____________________________
The formula in (a) is nitrogen monoxide. If there is only one of the more electropositive atoms, the “mono-“ prefix can be dropped. The “mono-“ prefix is always used for the more electronegative atom. In (b), no prefix on the sulfur implies one sulfur. Hexafluoride means six F-‘s. Therefore, the formula is SF6.
ACIDS
As a final note, we should talk about naming acids. You should be familiar with some common names, such as the following:
H2SO4 sulfuric acid
H3PO4 phosphoric acid
Most acids used in the laboratory can be classified as either binary or oxyacids (acids containing hydrogen, oxygen and a third element). All acids are named after the name of the anion. Three general rules apply:
- If the anion ends in –ide, then the acid is named hydro anion name-ic acid
- If the anion ends in –ate, then the acid is named anion name-ic acid
- If the anion ends in –ite, then the acid is named anion name-ous acid
For example,
HCl hydrochloric acid (from chloride)
HBr hydrobromic acid (from bromide)
HClO4 perchloric acid (from perchlorate ion)
HClO2 chlorous acid (from chlorite ion)
H2CrO4 chromic acid (from chromate ion)
HNO2 nitrous acid (from nitrite ion)
Most of the time, we will add the abbreviation for aqueous (aq) after the compound to indicate that it is dissolved in water and is, therefore, an acid. For instance, HI(aq) would be called hydroiodic aicd where as HI would be termed hydrogen iodide.
Nomenclature is an important part of the language of chemistry. Get used to naming these compounds. You’ll be seeing much more of them throughout the year!!!
Want more?
Download a lists of documents and tutorials of the related topics. Click the files below.
|
|