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• 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 nonmetals (upper right) on the periodic chart. Metaloids which border the stair-step transition line may behave as either positive or negative ions. 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 bromate bromite hypobromite BrO4-1 BrO3-1 BrO2-1 BrO-1 periodate iodate iodite hypoiodite IO4-1 IO3-1 IO2-1 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 chromate dichromate oxalate peroxide SO3-2 CrO4-2 Cr2O7-2 C2O4-2 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 nitrite hydroxide cyanide thiocyanate acetate Permanganate bicarbonate NO3-1 NO2-1 OH-1 CN-1 SCN-1 C2H3O2-1 MnO4-1 HCO3-1 Ions with a -2 Charge carbonate CO3-2 phthalate C8H4O4-2 sulfate SO4-2 sulfite chromate dichromate oxalate peroxide SO3-2 CrO4-2 Cr2O7-2 C2O4-2 O2-2 Ions with a -3 Charge phosphate PO4-3 phosphite PO3-3 arsenate AsO4-3 Ions with +1 charge ammonium ion NH4+1 Ions with -1 charge perbromate bromate bromite hypobromite perchlorate chlorate chlorite hypochlorite periodate iodate iodite hypoiodite BrO4-1 BrO3-1 BrO2-1 BrO-1 ClO4-1 ClO3-1 ClO2-1 ClO-1 IO4-1 IO3-1 IO2-1 IO-1 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 -1 -2 -3 -4 +3 +2 +1 0 7A 8A 1A H 2A Li Be 3A 4A 5A 6A Click on element to see its oxidation number(s) Na Mg K Ca Sc Ti Rb Sr Y V H He B C N O F Ne Al Si P S Cl Ar Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te Ce Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi I Xe 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 Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr 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”. 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 x +2 2. Determine the charge of the positive ion Cu The the positive You sum mustofknow the and negative charges charge on the sulfite must ion isequal -2 zero -2 = 0 SO3 X + (- 2)I’m = 0a +2 +2 polyatomic X = +2 ion copper (II) sulfite 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 KMnO4 I’m a polyatomic ion potassium(I) permanganate If the positive has a fixed Finalion Name charge, it is not shown 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 NH4NO3 ammonium(I) nitrate Finalion Name If the positive has a fixed charge, it is not shown I’m a polyatomic ion 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 SnF2 I’m not a polyatomic ion tin (II) fluoride 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 Ba(ClO4)2 I’m a polyatomic ion barium(II) perchlorate If the positive has a fixed Finalion Name charge, it is not shown 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 Cu2S I’m not a polyatomic ion copper (I) sulfide Final Name Examples #6- Formulas to Names 1.Write the names of the ions Cu2S (Cu+1x )2 S -2 2. Determine the charge of the positive ion The the the positive You sum mustofknow and negative charges charge on the sulfide must ion isequal -2 zero 2X + (- 2) = 0 +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 Na2Cr2O7 I’m a polyatomic ion sodium(I) dichromate If the positive has a fixed Finalion Name charge, it is not shown 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 Na2O2 I’m a polyatomic ion sodium(I) peroxide If the positive has a fixed Finalion Name charge, it is not shown Examples #9- Formulas to Names 1. Write the names of the ions 2. Determine the charge of the positive ion I’m a hydrated compound, X = +3this part will be named last X + (-3) = 0 Fex (PO3 -3) = 0 FePO3..3H O 33H22O I’m a polyatomic ion iron (III) phosphite tri hydrate 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 LiCN I’m a polyatomic ion lithium(I) cyanide If the positive has a fixed FinalionName charge, it is not shown 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 X 1 Y= 3 3X = 1y 1. Write symbols of elements 2. Determine number of ions X(+3) + y(-1) = 0 (Al+3 )x(Cl-1)y= 0 aluminum What is the Lowest If there is no Roman Common Multiple “LCM” of Numeral, to know 3 andyou 1. need Do not worry the fixed oxidation number of about the sign(+/-) the positive ion. Choose the lowest set of integers that satisfies the equation chloride Al1Cl 3 Formula If there is only one Final atom the “1” is not shown Next Example #1-Names to Formulas 1. Write symbols of elements aluminum chloride 2. Determine number of ions (Al+3 )x(Cl-1)y If there is no Roman X(+3) + y(-1) = 0 Remember allmust compounds Numeral, you know the For aluminum, What is the Lowest This For formula says that chloride, are neutral, thus oxidation number of the “LCM” of a 1 is multiplied Common Multiple the +3 of one Al a 3charge is multiplied 1(+3) + 3(-1) = 0 the total positive charge positive ion. times the +3 to give 3 and 1. Do not worry atom timeswill thecancel -1 tothe-3 give must equal the +3the charge about charge 3 sign(+/-) Cl atoms aafrom -3 charge total negative charge Al1Cl3 If there is only one atom Final Formula the “1” is not shown Next Example #2-Names to Formulas 1. Write symbols of elements 2. Determine number of ions X 1 Y= 2 2X = 1y X(+2) + y(-1) = 0 (Co+2)x(BrO3-1)y= 0 cobalt(II) bromate Choose the lowest set of integers that satisfies the equation BrO3)2 Co1(BrO If there Final is only one atom Formula the “1” is not shown Next Example #3-Names to Formulas 1. Write symbols of elements X 1 Y= 3 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 C2H3O2)3 Ni1(C Formula If thereFinal is only one atom the “1” is not shown Next Example #4-Names to Formulas 1. Write symbols of elements 2. Determine number of ions X 3 Y= 1 1X = 3y X(+1) + y(-3) = 0 (Li +1 )x(PO4-3)y= 0 If there is no Roman Choose lowest Numeral, youthe need to know set of integersnumber that of the fixed oxidation the equation the satisfies positive ion. lithium phosphate PO4)1 Li3(PO If thereFinal is only one atom Formula the “1” is not shown 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 Fe(NO3)3 Choose the correct name for the compound 1. Iron trinitrate 2. iron(I) nitrate 3. iron(III) nitrite 4. iron(III) nitrate 5. none of the above Periodic Chart Polyatomic Ions next problem Practice Problem #2 sodium chlorite Choose the correct formula for the compound 1. NaCl 2. NaClO 3. NaClO2 4. Na(ClO)2 5. none of the above Periodic Chart Prefixes next problem 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 chromate dichromate oxalate peroxide SO3-2 CrO4-2 Cr2O7-2 C2O4-2 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 Oxidation Numbers (most common) -2 -3 -4 +3 +2 +1 -1 0 1A H 2A Li +1 +2 Be Click on element to see its oxidation number(s) Na Mg K Ca Sc Ti Rb Sr +2 +3 Y V +2 +4 7A 3A 4A 5A 6A 8A H He B C N O F Ne Al Si P S Cl Ar Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te Ce Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi I Xe Po At Rn Fr Ra Ac Rf Db Sg Rh Hs Mt return Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr