Chemical Nomenclature is the systematic naming of chemical compounds. Here we examine just a few rules for chemical substances that can be named relatively easily.
- Name the cation (the more electropositive one) first and the anion (the more electronegative one) second.
- Monoatomic cations take their name from the element name.
- Monoatomic anions take their names from the first part of the element name and then add "-ide".
Cation Name H+ Hydrogen Na+ Sodium Al3+ Aluminum Anion Name H- Hydride Cl- Chloride O2- Oxide
What are the names for NaCl, MgO, and HBr?
NaCl = sodium chloride
MgO = magnesium oxide
HBr = hydrogen bromide
- When elements form more than one type of ionic compound Roman numerals are used to indicate the charge on the cation.
Fe2+ and O2- give FeO = Iron(II) Oxide Fe3+ and O2- give Fe2O3 = Iron(III) Oxide Sn2+ and Cl- give SnCl2 = Tin(II) Chloride Sn4+ and Cl- give SnCl4 = Tin(IV) Chloride
There is an older system of naming these compounds that uses the Latin name of the metal with the suffices of "-ic" and "-ous" to designate the higher and lower charge of the metal, respectively.
So the examples above would be, under the older system,
FeO = Ferrous Oxide Fe2O3 = Ferric Oxide SnCl2 = Stannous Chloride SnCl4 = Stannic Chloride
Here are some other examples
Ion Latin Name Systematic Name Au+ Aurous Gold(I) Au3+ Auric Gold(III) Cu+ Cuprous Copper(I) Cu2+ Cupric Copper(II)
- For polyatomic ions, you should memorize the names below.
Ion Name NH4+ ammonium OH- hydroxide CN- cyanide C2O42- oxalate Cr2O72- dichromate NO3- nitrate SO42- sulfate PO43- phosphate ClO- hypochlorite ClO3- chlorate MnO4- permanganate HSO4- hydrogen sulfate or bisulfate Hg22+ Mercury(I) C2H3O2- acetate SCN- thiocyanate CrO42- chromate NO2- nitrite SO32- sulfite CO32- carbonate AsO43- arsenate ClO2- chlorite ClO4- perchlorate HSO3- hydrogen sulfite or bisulfite HCO3- hydrogen carbonate or bicarbonate