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Naming Covalent Compounds & Their Lewis Dot Structures

Naming Covalent Compounds & Their Lewis Dot Structures. Mr. Shields Regents Chemistry U10 L03. Naming conventions. There are two conventions used for naming Binary Organic Compounds: Common Name usage Stock System Recall: We used the Stock System when we named Ionic compounds

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Naming Covalent Compounds & Their Lewis Dot Structures

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  1. Naming Covalent Compounds & Their Lewis Dot Structures Mr. Shields Regents Chemistry U10 L03

  2. Naming conventions • There are two conventions used for naming • Binary Organic Compounds: • Common Name usage • Stock System • Recall: We used the Stock System when we named • Ionic compounds • - Example Cr(NO3)3 is named Chromium (III) Nitrate • For Covalently bonded compounds it works pretty • Much the same

  3. Stock System • Rules for using the stock system to name • Covalent Compounds: • Place and Name the least electronegative element first • ex: SO2 not O2S • 2) Determine the Oxidation state of the 1st named element • ex: SO2 S= +4 • 3) Use Roman Numerals to designate the oxidation number • ex: SO2 is Sulfur (IV) • 4) Ending for the More electronegative element is –ide • ex: SO2 is Sulfur (IV) Oxide

  4. Stock Name Problems Using Stock System nomenclature name the following: CBr4 SO3 N2O5 N20 Carbon (IV) Bromide Sulfur (VI) Oxide Nitrogen (V) Oxide Nitrogen (I) oxide

  5. Common Name System In the Common naming system the following rules Apply: • Place and Name the least electronegative element first • (just like in the stock system) • ex: PCl3 not Cl3P • 2) Ending for the More electronegative element is –ide • (again just like the stock system) • ex: Chlorine  Chloride • 3) Here’s the difference: Specify the NUMBER OF ATOMS • as a prefix using the names in the following table…

  6. Common Covalent Prefixes Whats the Stock System name? (N ox. # =-3) Ex: Si3N4 =Trisilicon Tetranitride

  7. Some other Rules: The prefix “Mono” is Not added to the 1st Name of a compound Ex: CO is carbon monoxide Not Monocarbon Monoxide Also -> The “Fine Print”

  8. Common Name System Exceptions Here are some Common Name exceptions due to more familiar name usage: NH3 O2 H2O Ammonia not Nitrogen Trihydride Oxygen not Dioxide or Dioxygen (same is true for other diatomics) Water not Dihydrogen monoxide

  9. Common Name System Using common nomenclature name the following: CBr4 SO3 N2O5 P2S3 Carbon tetrabromide Sulfur trioxide Dinitrogen Pentoxide DiPhosphorous Trisulfide

  10. CH4 METHANE Drawing Lewis Dot Structures Lewis Dot structures show how atoms are connected, And what bonds are present by indicating the Placement of valence electrons Let’s look at the rules for drawing these structures

  11. Rules for Drawing Covalent Lewis Dot Structures • Rules: • Count the total number of valence electrons for all atoms • - CO2 1C = 4 electrons • + 2O= 12 electrons = 16 electrons • 2) Connect the atoms by single covalent bonds (make it • symmetrical if possible) • O – C – O Remember a single line represents 2e-

  12. . . .. . . .. :O – C – O: Rules for Drawing Covalent Lewis Dot Structures 3) Subtract the single bond electrons from the total number of electrons - CO2 16 electrons – 4 = 12 electrons 4) Add remaining electrons symmetrically as lone pairs DO THE TEST: DOES EVERY ATOM HAVE AN OCTET? - YES  You’re Done - NO  Move lone pairs into bonding positions

  13. :O – C – O: :O – C = O: :O – C = O: :O = C = O:  . . .. . . . . . . .. . . .. . . .. . . ..  TEST: Do all atoms have an octet? NO - Move lone pair into bonding position from other atom TEST: Do all atoms have an octet? YES - THEN YOU’RE DONE !

  14. Try the Following • Draw the Lewis dot structure for N2H2 • Count the total number of valence electrons for all atoms • - N2H2 2N = 10 electrons • + 2H = 2 electrons = 12 electrons • 2) Connect the atoms by single covalent bonds (make it • symmetrical if possible) • H – N – N - H Symmetrical and H can only share 2 electrons

  15. H - N – N - H Try the following 3) Subtract the single bond electrons from the total number of electrons H – N – N - H  12 electrons – 6 = 6 electrons 4) Add remaining electrons as lone pairs TEST: DOES EVERY ATOM HAVE AN OCTET? - NO?  Move lone pairs into bonding positions

  16. H - N – N - H H - N = N - H  .. .. .. .. .. RETEST: Do all atoms have an octet? YES – THEN YOU’RE DONE !

  17. Try This one: Draw the Lewis Dot Structure for SO3 .. .. :O:S::O: .... :O: ..

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