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Chemical Nomenclature

Chemical Nomenclature. In 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!

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Chemical Nomenclature

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  1. Chemical Nomenclature • In 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. 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 soledad Printable summary of nomenclature Flow chart double-click to open attachments

  2. ELEMENTS: symbols You 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 O3carbon: graphite, diamond

  4. BINARY IONIC COMPOUNDS • Binary = only 2 different elements present • Cation: retains name of element • Anion: suffix -ide oxide O2 fluoride F Metal + nonmetal NaCl = sodium chloride CaS = calcium sulfide AlF3 = aluminum fluoride

  5. Ca+2 F-1yields CaF2 12 Al+3 O-2yields Al2O3 23 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 O3 - 2Right: Al2O3 • Simplest formula must be given (ionic compounds only) • WRONG: Ca2O2Right: CaO

  6. : :O: : : :O-N=O: : POLYATOMIC IONS • Polyatomic ions are charged molecules held together by covalent bonds • They stay in one piece and behave as a single ion in many reactions • They are very common, so you must know their names! • Memorize name, formula and charge -1 Lewis structure of nitrate, a polyatomic ion (charged molecule)

  7. POLYATOMIC IONS to be memorized cation: ammonium NH4+1 -ides: hydroxide OH1 cyanide CN1 -ates: acetate C2H3O21 carbonate CO32 phosphate PO43 chromate CrO42 dichromate Cr2O72 permanganate MnO4-1 nitrate NO31 sulfate SO42 chlorate ClO31 -ites: nitrite NO21sulfite SO32

  8. POLYATOMIC IONS: naming compounds • The name of the polyatomic ion is retained in the name of the compound. Examples: Na2CO3 sodium carbonate NH4C2H3O2 ammonium acetate Practice: write the formula or name: sodium hydroxide Na2SO4 ammonium nitrate Na2Cr2O7 potassium phosphate AgCN Formulas: NaOH, NH4NO3, K3PO4 Names: sodium sulfate, sodium dichromate, silver cyanide

  9. POLYATOMIC IONS: anions containing H (acid salts) • Some anions add H+ to form hydrogen ___ ion. Examples: • PO43 phosphate • HPO42 hydrogen phosphate • H2PO41 dihydrogen phosphate • HS-1 hydrogen sulfide • HSO31 hydrogen sulfite • HSO41 hydrogen sulfate • HCO31hydrogen carbonate (a.k.a. bicarbonate) • Examples • NaHSO4 sodium hydrogen sulfate • KH2PO4 potassium dihydrogen phosphate • NaHCO3 sodium hydrogen carbonate (a.k.a. sodium bicarbonate)

  10. CHARGES of ions • Many elements always form ions with a certain charge. You should know these: • Group 1 form +1 ions • Group 2 form +2 ions • Group 3 form +3 ions • Group 16 form -2 ions • Group 17 form -1 ions • Ag +1 • Zn and Cd +2 • Cu +1 and +2 • Pb and Sn +2 and +4 • Fe +2 and +3 predictable from periodic table: no need to memorize these 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) chloride iron (III) = Fe+3, FeCl3 = iron (III) chloride • More examples chromium(III) oxide, copper(I) oxide, copper(II) oxide, tin(IV) oxide • Elements that form only 1 cation must not be identified with a Roman numeral. sodium oxide, magnesium oxide

  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. • Examples • Cr2O3 • Cr is a transition metal; oxidation number is 3 • Chromium (III) oxide • Al(NO3)3 • Al only forms +3 ions: no Roman numeral is needed • Aluminum nitrate [aluminum (III) nitrate is WRONG] • PbSO4 • Pb 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 • use prefixes mono, di, tri, tetra, penta, hexa... CO carbon monoxide CO2 carbon dioxide N2O dinitrogen monoxide P2O5 diphosphoruspentoxide ICl iodine monochloride GeO2 germanium dioxide • Note that “mono” is required for the second atom, but is dropped for the first. • A few important compounds have common names. MEMORIZE: NH3 = ammonia H2O = water H2O2 = hydrogen peroxide Two nonmetals in the formula and no charge

  14. BINARY MOLECULAR or IONIC? • If the compound contains a metal, it is named according to the rules for ionic compounds • If the compound contains 2 nonmetals, then it must be named using numeric prefixes. N2O3 dinitrogen trioxide NOT nitrogen (III) oxide Fe2O3 iron (III) oxide NOT diiron trioxide PbO2 lead (IV) oxide CO2 carbon dioxide AlF3 aluminum fluoride NOT aluminum trifluoride NF3 nitrogen trifluoride CaO calcium oxide NOT calcium monoxide NO 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 dioxide SO3–2 sulfite SO3 sulfur trioxide ClO2– chlorite ClO2 chlorine dioxide

  16. ACIDS Common acids you should know: HF hydrofluoric acid HCl hydrochloric acid HNO3 nitric acid HNO2 nitrous acid H2SO4 sulfuric acid H2SO3 sulfurous acid H3PO4 phosphoric acid HC2H3O2 acetic acid Formula starts with H

  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 anion • Binary: drop -ide and add hydro___ic acid • HCl: chloride hydrochloric acid • HI: iodide hydroiodic acid • Polyatomic anion: -ate becomes -ic acid, • -ite becomes -ous acid • HNO3 : nitrate nitric acid • HNO2 : nitrite nitrous acid • Slight 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 acid • HCl(g) = hydrogen chloride (gas--not dissolved in water) • Both H2S(g) and H2S(aq) are usually called hydrogen sulfide • The rest are always named as acids: • HNO3 nitric acid • H2SO4 sulfuric acid • H3PO4 phosphoric acid • HC2H3O2 acetic acid • etc. • These are never called • hydrogen ___ate.

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