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Chpt 7 part 1 - chemical nomenclature 042403

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Chpt 7 part 1 - chemical nomenclature 042403

  1. 1. ChemicalNomenclature Part I Rev. 032205
  2. 2. Chemists need asystematic way of naming compounds
  3. 3. 1. Prevent confusing one compound for anotherConsider these compounds: FeO and Fe2O3Iron (II) oxide and iron (III) oxide CO2 and COcarbon dioxide and carbon monoxide
  4. 4. 2. Formulas may be too complex to say.For carbon dioxide … … you can easily say CO2But would you like to say C6H4OCOCH3CO2H when you could say aspirin Or, even acetylsalicylic acid
  5. 5. 3. Families of compoundshave similarities in names and propertiesThe calcium carbonate in Tums is an antacid …… any carbonate compound will react with any acid.
  6. 6. Chemical names … Prevent confusing one compound for another Keep from having to say complex formulas Group compounds into families
  7. 7. The convention for writing formulas of simple inorganic compounds: The element with the positive oxidation number is written first.
  8. 8. A binary compound contains only two kinds of elements H2O and HCl CO2 and N2O5 NaCl and BiF3
  9. 9. Naming BinaryCompounds ofTwo Nonmetals
  10. 10. Naming a compound with only two nonmentals…1. Write the name of the first element along with the appropriate prefix.2. Write the name of the second element, modified to end in ide, along with the appropriate prefix.
  11. 11. Greek Prefixesmono- 1 hexa- 6di- 2 hepta- 7tri- 3 octa- 8tetra- 4 nona- 9penta- 5 deca- 10
  12. 12. -ide endingsHydrogen – hydride Sulfur – sulfideCarbon – carbide Chlorine – chlorideNitrogen – nitride Arsenic – arsenideOxygen – oxide Selenium – selenideFluorine – fluoride Bromine – bromideSilicon – silicide Tellurium – telluridePhosphorous – phosphide Iodine – iodide
  13. 13. Examples …NO2 nitrogen dioxidePCl3 phosphorous trichlorideAsI5 arsenic pentiodideN2O4 dinitrogen tetroxide triiodine heptanitrideI3N7
  14. 14. Use mono- sparinglyThe prefix mono- should only be used to prevent confusion … as in CO and CO2 Carbon monoxide and carbon dioxide
  15. 15. You can write the formula from thename. The prefix tells the subscript.  Nitrogen trichloride NCl3  Carbon tetrachloride CCl4  Diphosphorous pentoxide P 2O 5
  16. 16. Naming Binary CompoundsContaining a Metal and a Nonmetal
  17. 17. The Stock System Named for Alfred Stock, a German chemist of the nineteenth century. Add a Roman Numeral after the name of the positive element to indicate its oxidation number.
  18. 18. Using the Stock System:1. Write the name of the positive element2. Add a Roman numeral corresponding to the oxidation number of the positive element (if necessary)3. Write the name of the negative element, modified to end in -ide
  19. 19. When is the Roman Numeral Necessary? When the metal has more than one oxidation number. Metals in groups I A, II A, and III B, do not need Roman numerals. Others metals have several oxidation numbers, and need Roman numerals.
  20. 20. What is an oxidation number?An oxidation number is anumber that tells us how anelement combines with otherelements. For ions, the oxidation number is the ionic charge.
  21. 21. We can find oxidationnumbers in tables or wecan predict them using the periodic table.
  22. 22. What does the Roman Numeral do?  The Roman numeral indicates the oxidation number on a single metal atom, and differentiates between several possible compounds.  Consider: FeO and Fe2O3  Both contain iron and oxygen  But, both cannot be iron oxide …
  23. 23. … so we use a Romannumeral to differentiate between the two compounds.
  24. 24. First, determine the oxidationnumber of iron in FeO … … by starting with the negative element, find the oxidation number of the positive element. Since iron has an oxidation number of +2, FeO is named iron (II) oxide.
  25. 25. Likewise, for Fe2O3 …First, determine the oxidation numberof iron in Fe2O3 … … by starting with the negative element, find the oxidation number of the positive element.Since iron’s oxidation number is +3,Fe2O3 is named iron (III) oxide.
  26. 26. Remember … Only add a Roman Numeral if it is needed. It is needed when the metal has more than one positive oxidation number. If the element has only one positive oxidation number, you do not need a Roman numeral.
  27. 27. Writing formulas ofbinary compounds of a metal and a nonmental
  28. 28. The sum of the oxidationnumbers on all the atoms ina compound must equalzero. Consider iron (II) oxide. Oxygen is –2 +2 –2 = 0 and iron is +2. FeO The sum is 0.
  29. 29. Now consider iron (III) oxide In iron (III) oxide, +3 -2 the iron is +3 and Fe2O3 the oxygen is –2. These don’t add up to zero.
  30. 30. Now consider iron (III) oxide But, since there +6 -6 = 0 +3 -2 are two Fe atoms Fe2O3 and three O atoms, we can multiply to 2x3=6 get the totals. 3 x –2 = -6 Now the sum is zero.
  31. 31. Look at it another way: +6 –6 = 0 +6 -6 +3 +3 -2 -2 -2Fe2O3 = Fe Fe O O O
  32. 32. Now your areready to write formulas
  33. 33. The Crisscross MethodSimple but effective,…most of the time.Be aware of the potential problems with this method.
  34. 34. Suppose you are writing theformula for copper (II) chloride First, write down the symbols: Cu Cl
  35. 35. Then write the oxidationnumbers in copper (II) chlorideThe oxidation Get thenumber of oxidationcopper comes number offrom the +2 -1 chlorinename. Cu Cl from the periodic table.
  36. 36. Crisscross the numbers for theformula of copper (II) chloride When you crisscross, ignore the signs. +2 -1 Cu1 Cl 2
  37. 37. Clean up the subscripts in theformula of copper (II) chloride Subscripts of 1 are invisible. (don’t even put the 1) +2 -1 Cu1 Cl 2
  38. 38. Now you have the formula of copper (II) chloride Cu Cl 2
  39. 39. When is the “crisscross method” a problem?When all thesubscripts are divisibleby a number other than1.
  40. 40. Look at chromium (VI) oxide The oxidation +6 -2 number of Cr isCr O +6 Oxygen is always -2
  41. 41. Look at chromium (VI) oxide Now, crisscross the oxidation numbers. +6 -2 -2 Cr2 O6 When you crisscross, both subscripts are divisible by 2.
  42. 42. Look at chromium (VI) oxide Divide each subscript by 2. +6 -2 Cr__ O__ 2 6 2 2
  43. 43. Look at chromium (VI) oxide This is the correct formula Cr O3 Remember, 1’s are invisible.
  44. 44. Remember: reduce the subscripts to theirsmallest whole-number values. Unless there’s a really good reason not to.
  45. 45. Some Exceptions: C 2H 6 N2O4 C6H6 Hg2Cl2
  46. 46. The“ic/ous” Method of Naming Compounds
  47. 47. The “ic/ous” method …… is an archaic method, but still in use today by the chemical industry… uses the –ic or –ous suffixes on the name of the metal.… may use the Latin root… uses prefixes like hypo- & per-
  48. 48. Name and Lower Ox. Higher Ox.Latin Root Number Number iron ferrous ferricferrum Fe 2+ Fe 3+copper cuprous cupriccuprum Cu + Cu 2+mercury mercurous mercuric Hg22+ Hg2+
  49. 49. Higher oxidation number IC OUSLower oxidation number
  50. 50. Examples …FeCl2 Ferrous chlorideCuO Cupric oxideFeN Ferric nitrideCu3P Cuprous phosphideHgS Mercuric sulfideHg2Cl2 Mercurous chloride
  51. 51. Write the formula …Ferric bromide FeBr3Cupric nitride CuN3Ferrous chloride FeCl2Mercuric oxide HgOMercurous iodide Hg2I2Stannous fluoride SnF
  52. 52. Click on the links below for Parts II or IIIPart II – Polyatomic ionsPart III – Naming Acids and Bases

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