1 Mr. ShieldsRegents Chemistry U10 L03

2 There are two conventions used for naming Binary Organic Compounds: 1) Common Name usage 2) Stock System Recall: We used the Stock System when we named Ionic compounds - Example Cr(NO 3 ) 3 is named Chromium (III) Nitrate For Covalently bonded compounds it works pretty Much the same Naming conventions

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

4 Stock Name Problems Using Stock System nomenclature name the following: CBr 4 SO 3 N2O5N2O5 N20N20 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: 1)Place and Name the least electronegative element first (just like in the stock system) ex: PCl 3 not Cl 3 P 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 Atom name Prefix To designate this # of atoms Mono1 Di2 Tri3 Tetra4 Penta5 Hexa6 Hepta7 Octa8 Ex: Si 3 N 4 = Trisilicon Tetranitride Whats the Stock System name? (N ox. # =-3)

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

8 Common Name System Exceptions Here are some Common Name exceptions due to more familiar name usage: NH 3 O2O2 H2OH2O 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: CBr 4 SO 3 N2O5N2O5 P2S3P2S3 Carbon tetrabromide Sulfur trioxide Dinitrogen Pentoxide DiPhosphorous Trisulfide

10 Lewis Dot structures show how atoms are connected, And what bonds are present by indicating the Placement of valence electrons CH 4 METHANE Drawing Lewis Dot Structures Let’s look at the rules for drawing these structures

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

12 Rules for Drawing Covalent Lewis Dot Structures 3) Subtract the single bond electrons from the total number of electrons - CO 2  16 electrons – 4 = 12 electrons 4) Add remaining electrons symmetrically as lone pairs.... :O – C – O: DO THE TEST: DOES EVERY ATOM HAVE AN OCTET? - YES  You’re Done - NO  Move lone pairs into bonding positions

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

14 Try the Following Draw the Lewis dot structure for N 2 H 2 1)Count the total number of valence electrons for all atoms - N 2 H 2  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 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 H - N – N - H

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

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