Presentation on theme: "Chemical Nomenclature"— Presentation transcript:
1 Chemical Nomenclature El mundo era tan reciente, que muchas cosas carecían de nombre, y para mencionarlas había que señalarlas con el dedo.-G. García Márquez, Cien años de soledadIn Chem 110 and 111, you are asked to learn the names of a selection of simple but common compounds without which it’s pretty hard to carry on a conversation about chemistry.Nomenclature will account for about 10% of your grade in 111!Use my table of polyatomic ions instead of Tables 6-3, 6-5 and 6-6.Do not memorize Table 6-4.Printable summary of nomenclatureFlow chartdouble-click to open attachments
2 ELEMENTS: symbolsYou should already have memorized the names and symbols of these common elements!The significance of the blue elements is that they have more than one common oxidation number.
3 ELEMENTS: diatomics and allotropes Diatomic molecules are the most stable form for H2, N2, O2, F2, Cl2, Br2, I2. (blue shading below)You must know these to correctly write and balance chemical equations in the next chapter.Sometimes allotropes (alternate forms of the pure element) exist: oxygen: O2 ozone O3 carbon: graphite, diamond
4 BINARY IONIC COMPOUNDS Metal + nonmetalBinary = only 2 different elements presentCation: retains name of elementAnion: suffix -ideoxide O2 fluoride FNaCl = sodium chlorideCaS = calcium sulfideAlF3 = aluminum fluoride
5 BINARY IONIC COMPOUNDS: formula from name To write the correct formula from the name, you have to know the charges of the ions (chapter 5)The charges in the formula must add up to zero.shortcut: write the charges and swap them down (without signs):Charges must not appear in the finished formula!WRONG: Al2+3 O Right: Al2O3Simplest formula must be given (ionic compounds only)WRONG: Ca2O2 Right: CaOCa+2 F-1 yields CaF2Al+3 O-2 yields Al2O3
6 Polyatomic ions are charged molecules held together by covalent bonds They stay in one piece and behave as a single ion in many reactionsThey are very common, so you must know their names!Memorize name, formula and charge:O::O - N=O::-1Lewis structure of nitrate, a polyatomic ion(charged molecule)
8 POLYATOMIC IONS: naming compounds The name of the polyatomic ion is retained in the name of the compound.Examples:Na2CO3 sodium carbonateNH4C2H3O2 ammonium acetatePractice: write the formula or name:sodium hydroxide Na2SO4ammonium nitrate Na2Cr2O7potassium phosphate AgCNFormulas: NaOH, NH4NO3, K3PO4Names: sodium sulfate, sodium dichromate, silver cyanide
10 CHARGES of ionsMany elements always form ions with a certain charge. You should know these:Group 1 form +1 ionsGroup 2 form +2 ionsGroup 3 form +3 ionsGroup 16 form -2 ionsGroup 17 form -1 ionsAg +1Zn and Cd +2Cu +1 and +2Pb and Sn and +4Fe +2 and +3predictable from periodic table: no need to memorizethese are so common that you should memorize them
11 VARIABLE OXIDATION NUMBERS Most transition elements and some representative elements are capable of forming ions with several possible oxidation numbers.These are indicated in blue on the periodic table, page 2.For these elements, a Roman numeral is required to specify the oxidation number of the cation.iron (II) = Fe+2, FeCl2 = iron (II) chlorideiron (III) = Fe+3, FeCl3 = iron (III) chlorideMore exampleschromium(III) oxide, copper(I) oxide, copper(II) oxide, tin(IV) oxideElements that form only 1 cation must not be identified with a Roman numeral.sodium oxide, magnesium oxidejust ironis not en;ough
12 VARIABLE-CHARGE METALS: name from formula When given a formula to name, you must decide if the metal is one of the variable ones. If it is, then you must determine its oxidation number to name it properly.ExamplesCr2O3Cr is a transition metal; oxidation number is 3Chromium (III) oxideAl(NO3)3Al only forms +3 ions: no Roman numeral is neededAluminum nitrate [aluminum (III) nitrate is WRONG]PbSO4Pb is known to have variable oxidation number.Since sulfate has a charge of -2, Pb must have a charge of +2 in this compound.Lead (II) sulfate
13 BINARY MOLECULAR COMPOUNDS Two nonmetals in the formula and no chargeuse prefixes mono, di, tri, tetra, penta, hexa...CO carbon monoxide CO2 carbon dioxide N2O dinitrogen monoxide P2O5 diphosphorus pentoxideICl iodine monochloride GeO2 germanium dioxideNote that “mono” is required for the second atom, but is dropped for the first.A few important compounds have common names.MEMORIZE: NH3 = ammoniaH2O = waterH2O2 = hydrogen peroxide
14 BINARY MOLECULAR or IONIC? If the compound contains a metal, it is named according to the rules for ionic compoundsIf the compound contains 2 nonmetals, then it must be named using numeric prefixes.N2O3 dinitrogen trioxide NOT nitrogen (III) oxideFe2O3 iron (III) oxide NOT diiron trioxidePbO2 lead (IV) oxideCO2 carbon dioxideAlF3 aluminum fluoride NOT aluminum trifluorideNF3 nitrogen trifluorideCaO calcium oxide NOT calcium monoxideNO nitrogen monoxide
15 BINARY MOLECULAR COMPOUND or ion? If a charge is written ( NO2–) or implied (NaNO2) then you must use the polyatomic ion name.If there is no charge, ( NO2) then the compound should be named as a binary nonmetal compound.NO2– nitrite NO2 nitrogen dioxideSO3–2 sulfite SO3 sulfur trioxideClO2– chlorite ClO2 chlorine dioxide
16 Common acids you should know: HF hydrofluoric acid Formula starts with HCommon acids you should know:HF hydrofluoric acidHCl hydrochloric acidHNO3 nitric acidHNO2 nitrous acidH2SO4 sulfuric acidH2SO3 sulfurous acidH3PO4 phosphoric acidHC2H3O2 acetic acid
17 ACIDS (2)For this class, it is sufficient to memorize the acid names and formulas on the previous page. For your edification, here are name-formation rules:Start from the name of the anionBinary: drop -ide and add hydro___ic acidHCl: chloride hydrochloric acidHI: iodide hydroiodic acidPolyatomic anion: -ate becomes -ic acid,-ite becomes -ous acidHNO3 : nitrate nitric acidHNO2 : nitrite nitrous acidSlight spelling variations are found in the cases of sulfuric acid and phosphoric acid
18 ACIDS (3)HF, HCl, HBr, HI are named as acids only when dissolved in water Indicated by (aq)HCl(aq) = hydrochloric acidHCl(g) = hydrogen chloride (gas--not dissolved in water)Both H2S(g) and H2S(aq) are usually called hydrogen sulfideThe rest are always named as acids:HNO3 nitric acidH2SO4 sulfuric acidH3PO4 phosphoric acidHC2H3O2 acetic acidetc.These are never calledhydrogen ___ate.
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