Old System

The old naming system was one of the first methods of naming ionic compounds where the positive metal ion had two possible oxidation states. The “old method” was replaced by the much easier to use “stock system”. Chemical names are sometimes expressed in this old format. One should at least be able to recognize these old names when they are encountered, BUT the “Stock System” should be used when naming a compound.

The difficulty arises with the names and oxidation numbers of the positive metal ion in the compound name. Typically, for the name of the metal the old root word from whence the symbol of the metal was derived. For example, the original name for iron (symbol Fe) was ferrum. The two positive oxidation numbers of the different metal ions have different values. For example, iron has oxidation numbers of +2 and +3 while lead has oxidation numbers of +2 and +4.

The oxidation number the positive ion is characterized by the ending of the name of the positive ion. If the name ends in –ous then the ion has the lowest value of the two positive charges and if it ends in –ic it has the highest of the two charges. For example: ferrous chloride iron has a +2 charge FeCl2 iron(II) chloride (Stock System) ferric chloride iron has a +3 charge FeCl3 iron(III) chloride (Stock System)

Ferry boat to CoNi island @ 2 or 3. Fe (ferrum) iron +2/+3 Co cobalt +2/+3 Ni nickel +2/+3 Mnemonic Device Ferry boat to CoNi island @ 2 or 3. ferrous chloride Fe+2 FeCl2 ferric chloride Fe+3 FeCl3 cobaltous bromide Co+2 CoBr2 cobaltic bromide Co+3 CoBr3 nickelous sulfide Ni+2 NiS nickelic sulfide Ni+3 Ni2S3

Man Sitten in the Pub @2 or 4 Mn manganese +2/+4 Sn (stannum) tin +2/+4 Pb (plumbum) lead +2/+4 Mnemonic Device Man Sitten in the Pub @2 or 4 manganous nitrate Mn+2 Mn(NO3)2 manganic nitrate Mn+4 Mn(NO3)4 stannous fluoride Sn+2 SnF2 stannic fluoride Sn+4 SnF4 plumbous sulfate Pb+2 PbSO4 plumbic sulfate Pb+4 Pb(SO4)2

No Hugging of the Cuties @1 or 2 N nitrogen +1/+2 Hg mercury +1/+2 Cu copper cuprum +1/+2 Mnemonic Device No Hugging of the Cuties @1 or 2 nitrous oxide N+1 N2O nitric oxide N+2 NO mercurous carbonate Hg+1 Hg2CO3 mercuric carbonate Hg+2 HgCO3 cuprous nitride Cu+1 Cu3N cupric nitride Cu+2 Cu3N2

REMEMBER The only reason for this study of the old system is so that you can easily recognize this naming scheme. You should always use the stock system when writing the names of chemical compounds

Example #1-Names to Formulas ferric phosphate 1. Write symbols of elements. 2. What are the oxidation numbers? Fe PO4 ? ? +3 -3 3. Determine number of ions. Fe +1 -1 PO4 Remember all compounds are neutral, thus the total positive charge must equal the total negative charge This is the old naming system where the name ferric is derived from the root word ferrum which is the old name for iron. You must also remember that the polyatomic ion (PO4) has a -3 oxidation number This is the old naming system and the –ic ending of ferrum gives Fe a +3 oxidation number. Fe PO4 Final Formula Next

Example #2-Names to Formulas manganous oxide 1. Write symbols of elements. 2. What are the oxidation numbers? Mn O ? ? +2 -2 3. Determine number of ions. +1 Mn -1 O Remember all compounds are neutral, thus the total positive charge must equal the total negative charge You must also remember that oxygen has a -2 oxidation number This is the old naming system where the name manganous is derived from the root word manganese This is the old naming system and the –ous ending of manganous (manganese) gives Mn a +2 oxidation number. Mn O Final Formula Next

Cl -1 +1 Na -1 S +1 Ca Mn +1 Al +1 -1 N

Practice Problem #2 No, this is the formula for the -ic ending nitrous oxide Choose the correct formula for the compound 1. NO No, this is the formula for the -ic ending 2. NO2 No, this example does not follow Old System 3. N2O Very good, click arrow to continue 4. N2O2 No, this compound has too many oxygen atoms 5. none of the above No, there is a correct answer next problem Element List Old Names

Example #1-Names to Formulas This is the old naming system ferric phosphate 1. Write symbols of elements 2. Write number of atoms Fe PO4 If no prefix, then 1 is implied and not written Final Formula

Example #1-Names to Formulas I’m a Binary Compound Sulfur trioxide 1. Write symbols of elements S O 1 3 2. Write number of atoms If no prefix, then 1 is implied and not written Final Formula

Example #1-Names to Formulas I’m a Binary Compound Sulfur trioxide 1. Write symbols of elements S O 1 3 2. Write number of atoms If no prefix, then 1 is implied and not written Final Formula

Practice Problem #2 Very good, click arrow to continue arsenic pentabromide Choose the correct formula for the compound 1. AsBr5 Very good, click arrow to continue 2. ArBr5 No, "Ar" is not correct, see element list 3. AsBr7 No, you need to review prefixes 4. As5Br No, the subscript is with the wrong element 5. none of the above No, there is a correct answer next problem Element List Prefixes

Example #1-Names to Formulas aluminum chloride 1. Write symbols of elements. 2. What are the oxidation numbers? Al Cl ? ? +3 -1 3. Determine number of ions. Al +1 Cl -1 3 Remember all compounds are neutral, thus the total positive charge must equal the total negative charge If there is no Roman Numeral, you must know the oxidation number of the positive ion. Cl -1 You must also remember that chlorine is found in group 7A, which always has a minus one charge. How many chlorine ions would be needed to balance the +3 charge on the aluminum ion? Cl -1 If there is only one atom the “1” is not shown Al Cl 1 3 Final Formula Next

Example #1-Names to Formulas aluminum chloride 1. Write symbols of elements. 2. What are the oxidation numbers? Al Cl ? ? +3 -1 3. Determine number of ions. Al +1 Cl -1 3 Remember all compounds are neutral, thus the total positive charge must equal the total negative charge If there is no Roman Numeral, you must know the oxidation number of the positive ion. Cl -1 You must also remember that chlorine is found in group 7A, which always has a minus one charge. How many chlorine ions would be needed to balance the +3 charge on the aluminum ion? Cl -1 If there is only one atom the “1” is not shown Al Cl 1 3 Final Formula Next

Example #2-Names to Formulas Y 2 = 1. Write symbols of elements 2X = 1y X(+2) + y(-1) = 0 2. Determine number of ions (Co+2)x(BrO3-1)y= 0 cobalt(II) bromate Choose the lowest set of integers that satisfies the equation Co BrO3 (BrO3)2 1 If there is only one atom the “1” is not shown Final Formula