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Chapter 5 Nomenclature

Chapter 5 Nomenclature

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Chapter 5 Nomenclature

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  1. Chapter 5Nomenclature

  2. History of Naming • When chemistry first came about, there was no general naming system. • Scientists used common names like laughing gas, epsom salt, and milk of magnesia • This became impractical with the discovery of over 4 million chemical compounds • Therefore scientists developed a standardized system known as nomenclature

  3. Naming Binary Compounds • Binary compounds are composed of two elements • There are two classes • Compounds containing a metal & non-metal • Compounds containing two non-metals

  4. Naming Binary Ionic Compounds • Metals and non-metals combine to form compounds that contain ions (NaCl) • The metal loses 1 or more electrons to become a cation • The non-metal gains 1 or more electrons to became an anion • These are known as binary ionic compounds (ionic compounds for short)

  5. Naming Binary Ionic Compounds • There two types of binary ionic compounds • Type I: The metal present only forms one type of cation (Group IA, 2A, Al) • Type II: The metal can form two or more cations that have different charges (mostly transition metals like chromium, copper, etc)

  6. Naming Type I Binary Ionic Compounds • The rules are as follows • The cation is named first and the anion second. • A simple cation takes its name from the name of the element. • A simple anion takes the root name of the element and adds –ide to the end

  7. Example 1 • Name the following: NaCl • Rule 2: Name of cation is name of element: Sodium • Rule 3: Name of anion is element root with –ide: chloride • Rule 1: Cation first, anion second: Sodium Chloride

  8. Example 2 • Name the following: AlCl3 • Rule 2: Name of cation is name of element • Rule 3: Name of anion is element root plus –ide: • Rule 1: Cation first, anion second

  9. Now you try • Name the following • MgI2 • CaS Now we will try a few examples…

  10. Naming Type II Binary Ionic Compounds • There are many metals that can form more than one type of cation • Lead can form Pb2+ or Pb4+ • Iron can form Fe2+ or Fe3+ • Gold can form Au+ or Au3+

  11. Naming Type II Binary Ionic Compounds • Take AuCl vs. AuCl3 • If we named this using the rules for Type I compounds, Gold chloride, we wouldn’t know which formula the name was referring to • Chemists have solved this problem by using Roman Numerals to indicate the charge on a cation

  12. Naming Type II Binary Ionic Compounds • Consider FeCl2 • Fe can form Fe2+ or Fe3+ • Compounds containing ions must have a net charge of zero • Fe (?) Cl (-1 x 2 = -2) • Fe must 2+ • We name this compound Iron(II) chloride • Note: The Roman Numerals indicate the charge, NOT the number of atoms present

  13. Naming Type II Binary Ionic Compounds • The rules are as follows • Cation is named using element name • Charge is indicated by a Roman Numeral after the cation name • Anion is named using element root name and adding –ide

  14. Example 1 • Name the following: CuCl • We know that chlorine always forms -1 anions • Compounds containing ions must have a net charge of zero • Therefore copper must have a +1 charge • Name: Copper(I) chloride

  15. Example 2 • Name the following Fe2O3 • We know that oxygen always forms -2 anions, providing a total charge of -6 (-2 x 3) • Compound must have a net charge of 0 • Therefore iron must contribute +6 worth of charge • There are two iron atoms present, each having a charge of +3 • Name: Iron(III) oxide

  16. Now you try • PbCl4 • MnO2 • Now we will try a few examples…

  17. Naming Binary Compounds that Contain Only Non-metals (Type III) • Type III compounds only contain non-metals • These are known as non-ionic or covalent compounds

  18. Naming Type III Binary Compounds • The rules are as follows • The 1st element in the formula is named first. The full element name is used. • The 2nd element in the formula is named as if it were an anion (-ide ending) • Prefixes are used to denote the number of atoms present • The prefix mono- is never used for naming the first element

  19. Prefixes one mono two di three tri four tetra five penta six hexa seven hepta eight octa

  20. Example 1 • Name the following BF3 • Rule 1: Name the first element: boron • Rule 2: Name the second element like an anion: fluoride • Rule 3 & 4: Use prefixes for number of atoms • 1 boron atom (don’t use mono): boron • 3 fluorine atoms: trifluoride Name: boron trifluoride *Note: When the 2nd element is oxygen, we drop the a or o from the end of the prefix to avoid strange pronunciation

  21. Example 2 • Name the following N2O5 • Rule 1: Nitrogen • Rule 2: oxide • Rule 3 & 4 • 2 nitrogen: dinitrogen • 5 oxygen: pentoxide Name: dinitrogenpentoxide

  22. Now you try • CCl4 • IF5 • Now we will try a few examples

  23. Polyatomic Compounds • Polyatomic Ions are charge entities composed of several atoms bound together • Unfortunately, the names of most polyatomic atoms need to memorized

  24. Oxyanions • Oxyanions contain an atom of a given element and different numbers of oxygen atoms • Example SO4-2

  25. Oxyanions

  26. Some other common polyatomic ions • NH4+ Ammonium • OH- Hydroxide • CN- Cyanide • CO3-2 Carbonate

  27. Naming using polyatomic ions • Following typical naming rules • Cation named first, anion named second • Name of cation is element name • Name of anion is anion name • If a metal is present that is multivalent, we need to use Roman Numerals to indicate charge

  28. Example 1 • Na2SO4 • Name of cation is name of element: Sodium • Name of anion is anion name: sulfate • We know the charge on sodium, so we don’t need Roman numerals • Name: Sodium sulfate

  29. Example 2 • Fe(NO3)3 • Name of cation is name of element: Iron • Name of anion is anion name: nitrate • Need to calculate charge on copper: +3 • Name: Copper (III) nitrate

  30. You try • Mn(OH)2 • Na2SO3

  31. Naming Acids • When dissolved in water, certain compounds produce H+ ions • We call these compounds acids • Acids can be viewed as a compound with one or more H+ ions and an anion • Rules for naming depend on whether anion contains oxygen

  32. Naming Acid Rules • Does not contain oxygen: acid is named with the prefix hydro- and the suffix –ic Example: HCl Hydrochloric acid 2. Does contain oxygen: acid is named with the root name of the central element of the anion and a suffix a. When the anion name contain –ate, the suffix –ic is used i.e. H2SO4SO4 is sulfate sulfuric acid b. When the anion name contains –ite, the suffix –ous is used i.e. H2SO3 SO3 is sulfite sulfurous acid

  33. Example 1 • HBr • Does not contain oxygen • Hydrobromic acid

  34. Example 2 • HNO3 • Contains oxygen • NO3 is nitrate • Nitric acid

  35. You try • HI • H3PO3