Mr. Shields
Regents Chemistry
U10 L03
1
Naming conventions
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(NO3)3 is named Chromium (III) Nitrate
For Covalently bonded compounds it works pretty
Much the same
2
Stock System
Rules for using the stock system to name
Covalent Compounds:
1) 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
3
Stock Name Problems
Using Stock System nomenclature name the following:
CBr4
Carbon (IV) Bromide
SO3
Sulfur (VI) Oxide
N2O5
Nitrogen (V) Oxide
N20
Nitrogen (I) oxide
4
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: 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…
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Common Covalent Prefixes
Atom name Prefix
To designate
this # of atoms
Mono
1
Di
2
Tri
3
Tetra
4
Penta
5
Hexa
6
Hepta
7
Octa
8
Whats the Stock
System name?
(N ox. # =-3)
Ex: Si3N4 = Trisilicon Tetranitride
6
Some other Rules:
The prefix “Mono” is
Not added to the 1st
Name of a compound
Ex: CO is
Not
carbon monoxide
Monocarbon Monoxide
Also ->
The “Fine Print”
7
Common Name System Exceptions
Here are some Common Name exceptions due
to more familiar name usage:
NH3
Ammonia not Nitrogen Trihydride
O2
Oxygen not Dioxide or Dioxygen
(same is true for other diatomics)
H2O
Water not Dihydrogen monoxide
8
Common Name System
Using common nomenclature name the following:
CBr4
Carbon tetrabromide
SO3
Sulfur trioxide
N2O5
Dinitrogen Pentoxide
P2S3
DiPhosphorous Trisulfide
9
Drawing Lewis Dot Structures
Lewis Dot structures show how atoms are connected,
And what bonds are present by indicating the
Placement of valence electrons
CH4
METHANE
Let’s look at the rules for drawing these structures
10
Rules for Drawing Covalent Lewis
Dot Structures
Rules:
1) 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 2e11
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
..
..
:O
. . – C – O:
..
DO THE TEST: DOES EVERY ATOM HAVE AN OCTET?
- YES  You’re Done
- NO  Move lone pairs into bonding positions
12
..
..
: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 !
13
Try the Following
Draw the Lewis dot structure for N2H2
1) 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
14
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
H-N – N-H
TEST: DOES EVERY ATOM HAVE AN OCTET?
- NO?  Move lone pairs into bonding positions
15
..
..
H-N – N
.. - H

..
H-N = N
.. - H
RETEST: Do all atoms have an octet?
YES – THEN YOU’RE DONE !
16
Try This one:
Draw the Lewis Dot Structure for SO3
..
..
:O:S::O:
..
..
:O:
..
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