1. NOMENCLATURE OF INORGANIC COMPOUNDS Chapter VI

2. CHEMICAL FORMULAS Chemical formulas show the number of atoms present in eachcompound. AlCl3: One aluminum atom; three chlorine atoms Fe2(SO4)3: Two iron atoms; three sulfur atoms; twelve oxygenatoms KCl: One potassium atom; one chlorine atom Chemical formulas of ionic compounds represent the minimumnumber of atoms necessary to produce a neutral compound (formula unit): Ca2O2 is not a formula unit. The minimum number of atomsrequired to form this compound would be CaO. 3. OXIDATION NUMBER Oxidation Losing electrons Sodium atoms (Na) oxidize to form sodium cations (Na+) Fe2+ oxidizes to Fe3+ Reduction Gaining electrons Fluorine atoms (F) reduce to form fluoride anions (F-) Ag+ is reduced to Ag when it accepts one electron In ionic compounds, the oxidation number is the charge ofeach one of the ions present in the formula. The oxidation number of aluminum in the aluminum cation(Al3+) is +3 The oxidation number of sulfur in the sulfide anion (S2-) is -2 4. OXIDATION NUMBER Main group elements usually have a fixed oxidation number: Group 1A: +1 Group 2A: +2 Group 3A: +3 Group 4A: +4/-4 Group 5A: -3 Group 6A: -2 Group 7A: -1 Under special circumstances, some of these elements may haveother oxidation numbers. This is especially true for non-metals. 5. OXIDATION NUMBER GroupOxidation numberFrequency1A+1Always2A+2Always3A+3Always+4 and -4Most common+2 and -2Rare-3Most common+1, +2, +3, +4 or +5Rare-2Most common-1, +1, +2, +4, +6Rare-1Most common+1, +3, +5, +7Rare4A 5A 6A 7A 6. STOCK NOMENCLATURE Elements of the d-block and the f-block usually have a wide variety of oxidationnumbers and all of them are commonly found in nature. There are two iron oxides: FeO and Fe2O3 There are two copper oxides: CuO and Cu2O There are three chromium chlorides: CrCl2, CrCl3, CrCl4 For ions of elements that have multiple oxidation numbers, the stock system of nomenclature is used to name them. In the stock system, the oxidation number of the ion is written in parenthesis using roman numerals in front of the elements name: element(oxidation number) Fe2+ iron(II) Fe3+ iron(III) Cu+ --> copper(I) Mn7+ manganese(VII) Cr6+ chromium(VI) For ions of elements with characteristic oxidation numbers (alkali metals, alkaline earth metals, etc.) there is no need to write their oxidation number in parenthesis when naming them. (i.e. Na+ is called sodium) 7. STOCK NOMENCLATURE Elements whose oxidation numbers dont need to be stated in their stock nameElement(s)Oxidation numberGroup IA+1Group IIA+2Group IIIB+3Al, Ga, In+3Zn, Cd+2Ag+1 8. DETERMINING THE OXIDATION NUMBER OF A VARIABLE ELEMENT 1.Look for atoms in the formula that possess a constant oxidation number. (H and alkali metals +1; Alkaline earth metals +2; earth metals +3; oxygen -2). After this, identify the presence of elements with a variable oxidation number. 1.2.K2Cr2O7 (constant: K and O; variable: Cr)Write the charge of the known elements at the top of their positions in the formula unit. +1-2K2Cr2O7 9. DETERMINING THE OXIDATION NUMBER OF A VARIABLE ELEMENT 3.Multiply the charge of each of the known elements times the number of atoms of that element in the formula. Write the resulting number under the symbol of the element. DONT FORGET THE SIGN!! +1-2K2Cr2O7 +2-14-2x7 10. DETERMINING THE OXIDATION NUMBER OF A VARIABLE ELEMENT 4.Calculate the charge necessary so that the total sum of the charges is equal to zero (neutral). You may do this mentally or using algebra 4.Using algebra: +2+x-14=0 x-12=0 x=+125.Divide the resulting charge by the number of atoms present in the formula of the variable element. The resulting charge is the oxidation number of the variable element. +1 +6 -2K2Cr2O7 +2+12-14Divide +12/2= +6 11. WRITING CHEMICAL FORMULAS When writing the formulas of ionic compounds, the elements arewritten just as we write in English (from left to right) Cations always appear to the left of the formula Anions always appear to the right of the formula Al2O3 AgBr CuCl2 K2S The numbers written as a subscript in front of the symbol of the element are called stoichiometric numbers. These numbers represent the number of atoms of that element present in the formula. 12. FORMULAS WITH POLYATOMIC IONS An ion is a charged chemical species. As such, it is not limited tosingle atoms. Ions may be formed by more than one atom. These are calledpolyatomic ions. Another name for them is molecular ions, because the atoms in a polyatomic ion are bonded together by covalent bonds. 13. FORMULAS WITH POLYATOMIC IONS Polyatomic ions are treated as a whole; as an entity. When writing chemical formulas that include polyatomic ions; ifmore than one of such ions are needed to ensure neutrality, they must be written in parenthesis followed by the stoichiometric number to the right of the parenthesis. Fe3+ and SO42- Ba2+ and ClO3- Fe2(SO4)3Ba(ClO3)2 Na+ and NO3- NaNO3 (If only one is needed, the parenthesis is not necessary) NH4+ and S2- (NH4)2S 14. IUPAC NOMENCLATURE The International Union of Pure and Applied Chemistry (IUPAC) isthe organization in charge of standardizing chemical terminology and nomenclature. The IUPAC has set up some rules to name compounds accordingto their chemical function and composition. Types of chemical compounds: Binary: Formed by two different elements (NaI, HF, CaO, Al2S3) Ternary: Formed by three different elements (NaOH, BaSO4, HClO3) Quaternary: Formed by four different elements (NaHCO3) 15. IUPAC NOMENCLATURE OF BINARY COMPOUNDS 16. METAL OXIDES Metal oxides are formed by a metal cation and the oxide anion(O2-) Nomenclature: stock nomenclature of the metal ion +oxide Na2O sodium oxide MgO magnesium oxide Fe2O3 iron(III) oxide TiO2 titanium(IV) oxide 17. DETERMINING THE FORMULA FROM THE NAME OF THE COMPOUND 1.2.3. 4. 5. 6.Write the symbol of the elements that must be present in the formula according to the name of the compound. Cations are written first, then anions. From the name of the compound, deduce the charge of each ion. When metals have no explicit oxidation number in the name of the compound, its because its an element with a common or constant oxidation number. The oxidation number of variable elements is always stated in the name using stock nomenclature. Write the charges of each ion above their symbol. Cross the oxidation numbers of each ion and place them as the stoichiometric number with NO SIGN, JUST THE NUMBER. Simplify those numbers until you have the smallest ratio. Write the formula unit of the compound. 18. EXAMPLE 1.2.3.4. 5. 6.What is the formula of lead(II) oxide? Elements that must be in the formula: Pb and O The name implies this compound is a metal oxide because it only has oxygen and lead, which is a metal. The charge of the oxide anion is always -2; the charge of lead is revealed by its stock name (+2). Pb2+ O2Pb2+ O2- Pb2O2 As it stands, that formula is not the formula unit. The 2:2 ratio can be simplified to 1:1. Formula: PbO 19. NON-METAL OXIDES Non-metal oxides arise from the combination of a non-metal andoxygen. These compounds are NOT IONIC, they are molecularcompounds. As a consequence, their formulas are not called formula units, they are called molecular formulas. Molecular formulas dont have to show the minimal relationshipbetween the elements. (i.e. NO2 and N2O4 are two different chemical substances and both of them exist). 20. NON-METAL OXIDES Non-metal oxides are named the following way:prefix+non-metal+ prefix+oxide The prefix indicates how many atoms of each element are present in the formula. The prefixes refer to Greek numbering prefixes: 1 Mono 2 Bi- or di 3 Tri 4 Tetra 5 Penta 6 Hexa 7 Hepta 8 Octa 9 Nona 10 Deca- 21. NON-METAL OXIDES When there is only one atom of the non-metal in the formula, the mono-prefix is omitted. The mono- prefix is only used for oxygen. In the formula, the non-metal is written first, then the oxygen. Examples: NO: nitrogen monoxide CO2: carbon dioxide SO3: sulfur trioxide N2O: dinitrogen monoxide Cl2O7: dichlorine heptaoxide (also written as dichlorine heptoxide) Chemical formulas are very easy to deduce from the name of thecompounds because the number of atoms of each element is explicitly stated. 22. BINARY SALTS In chemistry, salt is a general term used to describe ioniccompounds resulting from a neutralization reaction. A neutralization reaction is one that occurs between an acid and a base. Binary salts contain a metal cation and a non-metal anion(other than the oxide anion) Examples: NaCl KI CaS AlCl3 23. BINARY SALTS Nomenclature: stock system name of the metal cation +root of the name of the non-metal + suffix ide Examples of roots for non-metals: Chlorine chlor + -ide chloride Bromine brom + -ide bromide Sulfur sulf + -ide sulfide Selenium selen + -ide selenide Phoshphorus phosph + -ide phosphide Nitrogen nitr + -ide nitride 24. BINARY SALTS Examples: RbCl rubidium chloride SrI2 strontium iodide Ag2S silver sulfide CdSe cadmium selenide LiF lithium fluoride AlP aluminum phosphide CuBr copper(I) bromide 25. BINARY SALTS In binary salts, the non-metal always has the characteristicoxidation number of its group. Group 14 anions -4 Group 15 anions -3 Group 16 anions -2 Group 17 anions -1 26. METAL HYDRIDES Metal hydrides are ionic compounds formed by the hydride anion(H-) and a metal cation. They are one of the few types of compounds in which hydrogenhas a charge of -1, instead of the usual +1. Ionic metal hydrides are only formed with metals of Group 1 and2. The rest of the metals form hydrides with a covalent nature. The nomenclature of such hydrides will not be discussed. Their nomenclature is similar to that of salts: stock systemname of the metal cation + hydride NaH sodium hydride CaH2 calcium hydride BeH2 beryllium hydride 27. NON-METAL HALIDES Halide is a term used to refer to salts where the anion is one ofthe halogens. Non-metal halides, however, are MOLECULAR. They contain one non-metal, other than hydrogen, bonded tohalogens. The nomenclature of these compounds is similar to that of non-metal oxides: numeric prefix+non-metal + numeric prefix + root of the name of the halogen + suffix ide CCl4 carbon tetrachloride PBr3 phosphorus triiodide SF4 sulfur tetrafluoride 28. BINARY ACIDS Also known as hydracids. They are formed by a non-metal and hydrogen. They are MOLECULAR compounds when in their pure state. Binary acids are usually soluble in water, and when theydissolve, their covalent bonds suffer electrolytic dissociation (they separate into ions). The aqueous solution of binary acids is acidic because of the presence of the hydrogen cation (H+). Given that hydracids may exist as molecular compounds oraqueous solutions; a nomenclature for each case has been developed. 29. BINARY ACIDS When binary acids exist as molecular compounds theirnomenclature is similar to the one of salts: hydrogen + root of the name of the non-metal + suffix ide Examples HCl hydrogen chloride H2S hydrogen sulfide HI hydrogen iodide H2Te hydrogen telluride 30. BINARY ACIDS When binary acids are present in aqueous solution: hydro- +root of the name of the non-metal + suffix ic + acid When binary acids are in aqueous solution, it is indicated in theformula with the (aq) subscript. Examples: HCl(aq) hydrochloric acid H2S(aq) hydrosulfuric acid HI(aq) hydroiodic acid H2Te(aq) hydrotelluric acid 31. IUPAC NOMENCLATURE OF TERNARY COMPOUNDS 32. METAL HYDROXIDES Metal hydroxides contain the polyatomic anion (OH)- called thehydroxide ion. The oxygen and the hydrogen in the hydroxide ion are bondedthrough a covalent bond. The oxygen possesses a negative charge. Metal hydroxides are named as follows: stock system name of the metal cation + hydroxide Examples: NaOH sodium hydroxide Mg(OH)2 magnesium hydroxide Mn(OH)2 manganese(II) hydroxide Au(OH)3 gold(III) hydroxide 33. OXOACIDS Oxoacids are composed of hydrogen, a non-metal, andoxygen. They are MOLECULAR compounds. Like other acids, oxoacids dissociate in aqueous solution that areacidic due to the presence of the hydrogen cation. The nomenclature of oxoacids is very particular because eachnon-metal may produce more than one oxoacid. This is determined by the amount of oxygen present in the formula. For example, chlorine produces four different oxoacids: HClO,HClO2, HClO3, and HClO4. 34. OXOACIDS Nomenclature: prefix- + root of the name of the non-metal +suffix + acid For oxoacids, the prefixes and suffixed denote the relativeamount of oxygen present in the formula. These prefixes and suffixes are not the Greek ones denoting numbers, they are: MeaningPrefixSuffixLowestHypo--ousLow-ousHigh-icHighestPer--ic 35. OXOACIDS Given that the prefixes and suffixes are related to somethingrelative, rules have been developed to assign the correct affix to each compound. This is done by determining the oxidation number of the non-metal Group IVAGroup VIAGroup VIIANomenclature+1+2+1Hypo___ous acid+3 +4Group VA+4+3____ous acid+5+6+5_____ic acid+7Per____ic acid 36. OXOACIDS The oxidation number of the non-metal can be determined usingthe usual method by assuming the compound is ionic. Example: Determine the oxidation number of chlorine in HClO3+1 +5 -2 (+1)(1)HClO3(-2)(3)+1 +5 -6 =0 +5/1 Since chlorine belongs to group VIIA and has an oxidation number of +5 , this compound is called chloric acid 37. OXYSALTS Oxysalts are IONIC compounds derived from the neutralization ofan oxoacid and a base. Oxysalts contain a metal cation and an oxyanion, which is thepolyatomic anion derived from the oxoacid. HClO3 ClO32- H2SO4 SO4 The charge of the polyatomic anion can be deduced bydetermining the oxidation number of the elements and adding the total charge (it will be less than zero in this case). An easier way to do it is by looking at how many hydrogen atoms were removed from the original oxoacid. The number of hydrogen atoms removed is the number of negative charges the anion has. 38. OXYSALTS The nomenclature of oxysalts is similar to that of binary salts:stock system name of the metal cation + name of the oxyanion The name of the oxyanion uses similar affixes than the ones usedfor oxoacids and depend of the oxidation number of the nonmetal. Group IVAGroup VIAGroup VIIANomenclature+1+2+1Metal Hypo___ite+3+4Group VA+4+3Metal ____ite+5+6+5Metal _____ate+7Metal Per____ate 39. OXYSALTS Examples: NaClO sodium hypochlorite K2CO3 potassium carbonate Mn(NO3)2 manganese(II) nitrate Al2(SO3)3 aluminum sulfite Ba(ClO4)2 barium perchlorate 40. OTHER POLYATOMIC IONS Cyanide anion (CN)- Permanganate anion (MnO4) Chromate anion (CrO4)-2- Dichromate anion (Cr2O7)2 Azide anion (N3)- The compounds formed by these ions with metal ions orhydrogen are named just like any other salt. NaN3 sodium azide KMnO4 potassium permanganate HCN hydrogen cyanide 41. OTHER POLYATOMIC IONS + The ammonium ion (NH4) is a cation derived from ammonia. Itforms salts with practically all anions. These salts are named like any other salt. (NH4)2S ammonium sulfide (NH4)2CO3 ammonium carbonate NH4ClO4 ammonium perchlorate 42. OTHER POLYATOMIC IONS Mercury has two oxidation numbers, +1 and +2. When in the +2state, it exists as a monoatomic cation as usual (Hg2+). However, when it is in its +1 oxidation state, it exists as a polyatomic cation (Hg2)2+. In this cation there is a covalent bond between the mercury atoms, and each one is has an oxidation number of +1. The name of this cation is mercury(I). Hg2Cl2 Mercury(I) chloride Hg2O Mercury (I) oxide