Nomenclature
Ionic Chemical Compounds
1. Name the cation (the more electropositive one) first and the anion (the more electronegative one) second. 2. Monoatomic cations take their name from the element name. 3. 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 O2Oxide
4. 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 5. So the examples above would be, under the older system, FeO = Ferrous Oxide Fe2O3 = Ferric Oxide SnCl2 = Stannous Chloride SnCl4 = Stannic Chloride 6. Here are some other examples Ion Au+ Au3+ Cu+ Cu2+ Latin Name Aurous Auric Cuprous Cupric Systematic Name Gold(I) Gold(III) Copper(I) Copper(II)
7. For polyatomic ions, you should memorize the names below.
Ion NH4+ OHCNC2O42Cr2O72NO3SO42PO43ClOClO3 MnO4HSO4Hg22+ C2H3O2SCNCrO42NO2SO32CO32AsO43ClO2 ClO4 HSO3HCO3-
Name ammonium hydroxide cyanide oxalate dichromate nitrate sulfate phosphate hypochlorite chlorate permanganate hydrogen sulfate or bisulfate Mercury(I) acetate thiocyanate chromate nitrite sulfite carbonate arsenate chlorite perchlorate hydrogen sulfite or bisulfite hydrogen carbonate or bicarbonate Binary Covalent Compounds
When a pair of elements form more than one type of covalent compound, Greek prefixes are used to indicate how many of each element are in a compound. For example: Compound N2O NO N2O3 N2O5 Name dinitrogen monoxide nitrogen monoxide dinitrogen trioxide dinitrogen pentoxide
Some of the Greek prefixes are given in the table below:
Prefix Mono Di Tri Tetra Penta Hexa Hepta Octa
Number of Particular Element 1 2 3 4 5 6 7 8
Rules for Binary Covalent Compounds 1. The prefix mono is never used for naming the element first of a compound. 2. The final o or a of a prefix is often dropped when the element begins with a vowel. For example, for CO the name will be carbon monoxide, and the final o of mono is dropped. Remember, it's only the final o or a. So, the name of ClO2 will be chlorine dioxide, and no vowels are dropped. How do you know which element goes first? The element that comes first in the following list "goes" first.
B, Si, C, Sb, As, P, N, H, Te, Se, S, I, Br, Cl, O, F
Finally, H2O, which according to the rules should be called dihydrogen monoxide is always called water, and NH3, or nitrogen trihydride, is always called ammonia. Naming Acids, Oxyacids and Their Salts 1. If the anion does not contain oxygen, then the acid is named with the prefix hydro- and the suffix -ic. o For example, when gaseous HCl is dissolved in H2O, it forms hydrochloric acid. o HCN in H2O is hydrocyanic acid. Before we learn the rule for naming oxyacids, let's learn the rules for naming oxyanions. What are oxyanions? They are anions formed from oxygen and a nonmetal. Here are some examples: ClO4-, ClO3-, ClO2-, ClO-, SO42-, SO32-. There are two rules for naming these:
2. If there are only two members in the same series, then the anion with the least number of oxygens ends in -ite, and the anion with the most ends in -ate. 22o For example, SO3 is sulfite and SO4 is sulfate. 3. When there are more than two oxyanions in a series, hypo- (less than) and per- (more than) are used as prefixes. Here are some examples: o ClO is hypochlorite o ClO2 is chlorite o ClO3 is chlorate o ClO4 is perchlorate Finally, here are the rules for naming acids of oxyanions. 4. If the anion name ends in -ate, then the acid name ends in -ic or -ric. 5. If the anion name ends in -ite, then the acid name ends in -ous. Here are examples of the last three rules: Acid Name hypochlorous HClO hypochlorite acid HClO2 chlorite chlorous acid HClO3 chlorate chloric acid HClO4 perchlorate perchloric acid Acid Anion