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Chemical Nomenclature

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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 soledad 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. 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 O3 carbon: graphite, diamond

4 BINARY IONIC COMPOUNDS
Metal + nonmetal Binary = only 2 different elements present Cation: retains name of element Anion: suffix -ide oxide O2 fluoride F NaCl = sodium chloride CaS = calcium sulfide AlF3 = 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: Al2O3 Simplest formula must be given (ionic compounds only) WRONG: Ca2O2 Right: CaO Ca+2 F-1 yields CaF2 Al+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 reactions They are very common, so you must know their names! Memorize name, formula and charge :O: :O - N=O: : -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 dichromate Cr2O72 permanganate MnO4-1 nitrate NO31 sulfate SO42 chlorate ClO31 -ites: nitrite NO2 sulfite 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 hydrogen sulfide HSO31 hydrogen sulfite HSO41 hydrogen sulfate HCO31 hydrogen 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 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 just 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. 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
Two nonmetals in the formula and no charge use prefixes mono, di, tri, tetra, penta, hexa... CO carbon monoxide CO2 carbon dioxide N2O dinitrogen monoxide P2O5 diphosphorus pentoxide 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

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 Common acids you should know: HF hydrofluoric acid
Formula starts with H 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

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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