NOMENCLATURE OF IONIC COMPOUNDS

Ionic compounds contain positive and negative ions Ionic compounds contain positive and negative ions. They are held together by electrostatic attraction. Most of the negative ions have only one possible oxidation state. This is not the case with the positive ions. Many of these ions have several oxidation states. The use of prefixes in naming these compounds could lead to confusion. Consequently a new method “the stock system” is very specific in the naming of ionic compounds.

Ionic compounds may contain (1) a metal and a non-metal, (2) a metal and a polyatomic ion or (3) a positive polyatomic ion and a negative polyatomic ion. No matter which is used the procedure for the “stock system is the same. The most difficult issue when using the “stock system” is the memorization of polyatomic ions and their oxidation states. The most common must be committed to memory. Look for trends.... Note location of metals (lower left) and non-metals (upper right) on the periodic chart. Metaloids which border the stair-step transition line may behave as either positive or negative ions.

The next table contains the polyatomic For example the oxy-salts of chlorine, bromine and iodine have many trends in common. Look for them below…… perchlorate ClO4-1 chlorate ClO3-1 chlorite ClO2-1 hypochlorite ClO-1 perbromate BrO4-1 bromate BrO3-1 bromite BrO2-1 hypobromite BrO-1 periodate IO4-1 iodate IO3-1 iodite IO2-1 hypoiodite IO-1 The next table contains the polyatomic ions that need to be committed to memory. Remember to learn the name, formula and oxidation number

POLYATOMIC IONS Ions with -1 charge perbromate BrO4-1 bromate BrO3-1 bromite BrO2-1 hypobromite BrO-1 perchlorate ClO4-1 chlorate ClO3-1 chlorite ClO2-1 hypochlorite ClO-1 periodate IO4-1 iodate IO3-1 iodite IO2-1 hypoiodite IO-1 nitrate NO3-1 nitrite NO2-1 hydroxide OH-1 cyanide CN-1 thiocyanate SCN-1 acetate C2H3O2-1 Permanganate MnO4-1 bicarbonate HCO3-1 Ions with a -2 Charge carbonate CO3-2 phthalate C8H4O4-2 sulfate SO4-2 sulfite SO3-2 chromate CrO4-2 dichromate Cr2O7-2 oxalate C2O4-2 peroxide O2-2 Ions with a -3 Charge phosphate PO4-3 phosphite PO3-3 arsenate AsO4-3 Ions with +1 charge ammonium ion NH4+1

POLYATOMIC IONS Ions with -1 charge perbromate BrO4-1 bromate BrO3-1 bromite BrO2-1 hypobromite BrO-1 perchlorate ClO4-1 chlorate ClO3-1 chlorite ClO2-1 hypochlorite ClO-1 periodate IO4-1 iodate IO3-1 iodite IO2-1 hypoiodite IO-1 nitrate NO3-1 nitrite NO2-1 hydroxide OH-1 cyanide CN-1 thiocyanate SCN-1 acetate C2H3O2-1 Permanganate MnO4-1 bicarbonate HCO3-1 Ions with a -2 Charge carbonate CO3-2 phthalate C8H4O4-2 sulfate SO4-2 sulfite SO3-2 chromate CrO4-2 dichromate Cr2O7-2 oxalate C2O4-2 peroxide O2-2 Ions with a -3 Charge phosphate PO4-3 phosphite PO3-3 arsenate AsO4-3 Ions with +1 charge ammonium ion NH4+1

BrO4-1 BrO3-1 BrO2-1 BrO-1 ClO4-1 ClO3-1 ClO2-1 ClO-1 IO4-1 IO3-1 IO2-1 IO-1 Ions with -1 charge perbromate bromate bromite hypobromite perchlorate chlorate chlorite hypochlorite periodate iodate iodite hypoiodite

It is also important to memorize the oxidation of the monatomic ions that have fixed oxidation numbers (positive or negative). In particular, those from groups 1A, 2A, 3A, 4A, 5A, 6A, 7A, 8A and the elements: Zn, Cd and Ag. Use the following periodic chart to determine their oxidation numbers. Just click on the element symbol…

Elements with Fixed Oxidation Numbers -3 -2 -4 +2 +1 -1 +3 1A 7A 8A H H He 2A 3A 4A 5A 6A Li Be B C N O F Ne Click on element to see its oxidation number(s) Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Ce Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Rf Db Sg Rh Hs Mt Nd Pm Sm Eu Gd Tb Ce Pr Yb Lu Dy Ho Er Tm Np Am Cm Bk Th Pa No Lr Cf Es Fm Md U Pu Next Slide

Naming Ionic Compounds The positive ion (usually a metal) is named first while the negative ion (a non-metal or a polyatomic ion) is named last. The charge on the negative ion is used to determine the charge on the positive ion. The oxidation state of a compound is always zero, otherwise it would be a polyatomic ion. In-order for the total oxidation state to be zero the total positive charge must equal the total negative charge. A simple algebraic equation can be used to determine the charge on a single metal ion. This charge is expressed as a “Roman Numeral” in parenthesis that immediately follows the name of the metal. If the positive ion is one that has a fixed oxidation number then no Roman Numeral is used. Everyone should know the charge of that ion. These include metals in group 1A, 2A and the specific metals: Al, Zn, Cd & Ag.

If the ionic compound is binary it will end in “-ide” If the ionic compound is binary it will end in “-ide”. However, not all compounds that end in “-ide” are binary. For example sodium hydroxide has the formula…NaOH (three different kinds of atoms). If the negative ion is a polyatomic ion the compound is no longer binary. The ending will be that carried by the polyatomic ion. These endings are either “-ate” or “-ite.” Hydrated compounds are named using a combination of both the stock system and prefixes. A prefix is used to denote the number of water molecules attached to the ionic formula. “hydrate” is used as the name indicating that water is attached. For example, copper(II) sulfate pentahydrate has the formula CuSO4.5H2O

Examples #1- Formulas to Names 1. Write the names of the ions CuSO3 -2 = 0 2. Determine the charge of the positive ion Cu +2 SO3 x X + (- 2) = 0 I’m a polyatomic ion The sum of the positive and negative charges must equal zero You must know the charge on the sulfite ion is -2 +2 +2 X = +2 copper sulfite (II) Final Name Next

Examples #2- Formulas to Names 1. Write the names of the ions 2. Determine the charge of the positive ion X = +1 X + (-1) = 0 Kx (MnO4)-1 = 0 I’m a polyatomic ion KMnO4 potassium permanganate (I) If the positive ion has a fixed charge, it is not shown Final Name

Examples #3- Formulas to Names 1. Write the names of the ions 2. Determine the charge of the positive ion X = +1 X + (-1) = 0 NH4x (NO3)-1 = 0 I’m a polyatomic ion NH4NO3 ammonium nitrate (I) If the positive ion has a fixed charge, it is not shown Final Name

Examples #4- Formulas to Names 1. Write the names of the ions 2. Determine the charge of the positive ion X = +2 X + 2(-1) = 0 Snx (F-1)2 = 0 I’m not a polyatomic ion SnF2 tin fluoride (II) Final Name

Examples #5- Formulas to Names 1. Write the names of the ions 2. Determine the charge of the positive ion X = +2 X + 2(-1) = 0 Bax (ClO4-1)2 = 0 I’m a polyatomic ion Ba(ClO4)2 barium perchlorate (II) If the positive ion has a fixed charge, it is not shown Final Name

Examples #6- Formulas to Names 1. Write the names of the ions 2. Determine the charge of the positive ion X = +1 2X + (-2) = 0 2Cux (S)-2 = 0 I’m not a polyatomic ion Cu2S copper sulfide (I) Final Name

Examples #6- Formulas to Names 1. Write the names of the ions Cu2S -2 2. Determine the charge of the positive ion (Cu )2 +1 S x 2X + (- 2) = 0 The sum of the positive and negative charges must equal zero You must know the charge on the sulfide ion is -2 +2 +2 2X = +2 2 2 X = +1 copper (I) sulfide Final Name Next

Examples #7- Formulas to Names 1. Write the names of the ions 2. Determine the charge of the positive ion X = +1 2X + (-2) = 0 2(Nax)(Cr2O7)-2 = 0 I’m a polyatomic ion Na2Cr2O7 sodium dichromate (I) If the positive ion has a fixed charge, it is not shown Final Name

Examples #8- Formulas to Names 1. Write the names of the ions 2. Determine the charge of the positive ion X = +1 2X + (-2) = 0 2(Nax) (O2-2) = 0 I’m a polyatomic ion Na2O2 sodium peroxide (I) If the positive ion has a fixed charge, it is not shown Final Name

Examples #9- Formulas to Names 1. Write the names of the ions I’m a hydrated compound, this part will be named last 2. Determine the charge of the positive ion X = +3 X + (-3) = 0 Fex (PO3 -3) = 0 I’m a polyatomic ion FePO3 .3H2O .3H2O 3 iron phosphite hydrate tri (III) Final Name

Examples #10- Formulas to Names 1. Write the names of the ions 2. Determine the charge of the positive ion X = +1 X + (-1) = 0 Lix (CN-1) = 0 I’m a polyatomic ion LiCN lithium cyanide (I) If the positive ion has a fixed charge, it is not shown Final Name

Writing Ionic Formulas It is easier to write the formula of an ionic compound from its name than the reverse. The oxidation state (or charge) of all compounds is zero. This is the first naming system that requires the balancing of the positive and negative charges such that the result is zero. The oxidation number of the negative ion must be memorized in all cases. Refer to the table of polyatomic ions.

The positive ion is either one of those that has a fixed oxidation number or a “Roman Numeral” will follow the positive ion. Metals that have only one oxidation number must be memorized. These include metals in group 1A, 2A and the specific metals: Al, Zn, Cd & Ag. If there is a “Roman Numeral” is in the name, it represents the charge of one of the positive ions.

Remember the total positive charge must equal to the total negative charge. The result is a compound which has no charge. Multiply the oxidation numbers of both the positive and negative ions by a number that will result in the smallest identical numbers of positive and negative charges. These multipliers represent the number of atoms of each ion required to give a neutral ionic compound.

The formulas of hydrated compounds are written using a combination of both the stock system and prefixes. A prefix is used to denote the number of water molecules attached to the ionic formula. “hydrate” is used as the name indicating that water is attached. For example, copper(II) sulfate pentahydrate has the formula CuSO4.5H2O (notice a dot separates the ionic compound from the water of hydration)

Example #1-Names to Formulas Y 3 X 1 = 1. Write symbols of elements 3X = 1y X(+3) + y(-1) = 0 2. Determine number of ions (Al )x(Cl-1)y= 0 +3 What is the Lowest Common Multiple “LCM” of 3 and 1. Do not worry about the sign(+/-) aluminum chloride If there is no Roman Numeral, you need to know the fixed oxidation number of the positive ion. If there is no Roman Numeral, you need to know the fixed oxidation number of the positive ion. Choose the lowest set of integers that satisfies the equation Al Cl 1 3 If there is only one atom the “1” is not shown Final Formula Next

Example #1-Names to Formulas aluminum chloride 1. Write symbols of elements 2. Determine number of ions (Al )x(Cl-1)y +3 If there is no Roman Numeral, you must know the oxidation number of the positive ion. If there is no Roman Numeral, you must know the oxidation number of the positive ion. What is the Lowest Common Multiple “LCM” of 3 and 1. Do not worry about the sign(+/-) What is the Lowest Common Multiple “LCM” of 3 and 1. Do not worry about the sign(+/-) For aluminum, a 1 is multiplied times the +3 to give a +3 charge Remember all compounds are neutral, thus the total positive charge must equal the total negative charge For chloride, a 3 is multiplied times the -1 to give a -3 charge This formula says that the +3 charge of one Al atom will cancel the-3 charge from 3 Cl atoms X(+3) + y(-1) = 0 1(+3) + 3(-1) = 0 Al Cl 1 3 If there is only one atom the “1” is not shown 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 Next

Example #3-Names to Formulas Y 3 = 1. Write symbols of elements 3X = 1y X(+3) + y(-1) = 0 2. Determine number of ions (Ni+3)x(C2H3O2-1)y= 0 nickel(III) acetate Choose the lowest set of integers that satisfies the equation Ni (C2H3O2)3 C2H3O2 1 If there is only one atom the “1” is not shown Final Formula Next

Example #4-Names to Formulas Y 1 = 1. Write symbols of elements 1X = 3y X(+1) + y(-3) = 0 2. Determine number of ions (Li )x(PO4-3)y= 0 +1 lithium phosphate If there is no Roman Numeral, you need to know the fixed oxidation number of the positive ion. If there is no Roman Numeral, you need to know the fixed oxidation number of the positive ion. Choose the lowest set of integers that satisfies the equation Li (PO4)1 PO4 3 If there is only one atom the “1” is not shown Final Formula Next

Practice Problems By now you should have an idea of what is expected when naming covalent binary compounds using prefixes. In order to master this naming system you need to practice until you feel proficient in naming compounds using prefixes.

Practice Problem #1 No, you do not use prefixes Fe(NO3)3 Choose the correct name for the compound 1. Iron trinitrate No, you do not use prefixes 2. iron(I) nitrate No, you have the wrong oxidation number 3. iron(III) nitrite No, you need to review polyatomic ions 4. iron(III) nitrate Very good, click arrow to continue 5. none of the above No, there is a correct answer next problem Periodic Chart Polyatomic Ions

Practice Problem #2 No, you need to review prefixes sodium chlorite Choose the correct formula for the compound 1. NaCl No, you need to review prefixes 2. NaClO No, you need to review prefixes 3. NaClO2 Very good, click arrow to continue 4. Na(ClO)2 No, you have several errors 5. none of the above No, there is a correct answer next problem Periodic Chart Prefixes

POLYATOMIC IONS return Ions with -1 charge perbromate BrO4-1 bromite BrO2-1 hypobromite BrO-1 perchlorate ClO4-1 chlorate ClO3-1 chlorite ClO2-1 hypochlorite ClO-1 periodate IO4-1 iodate IO3-1 iodite IO2-1 hypoiodite IO-1 nitrate NO3-1 nitrite NO2-1 hydroxide OH-1 cyanide CN-1 thiocyanate SCN-1 acetate C2H3O2-1 Permanganate MnO4-1 bicarbonate HCO3-1 Ions with a -2 Charge carbonate CO3-2 phthalate C8H4O4-2 sulfate SO4-2 sulfite SO3-2 chromate CrO4-2 dichromate Cr2O7-2 oxalate C2O4-2 peroxide O2-2 Ions with a -3 Charge phosphate PO4-3 phosphite PO3-3 arsenate AsO4-3 Ions with +1 charge ammonium ion NH4+1 return

Click on element to see its oxidation number(s) Oxidation Numbers (most common) -3 -2 +2 +1 -1 +3 -4 +1 +2 +2 +3 +2 +4 1A 7A 8A H H He 2A 3A 4A 5A 6A Li Be B C N O F Ne Click on element to see its oxidation number(s) Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Ce Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Rf Db Sg Rh Hs Mt Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu return Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr