# Practice Set on Writing Electron Dot Formulas Lewis Diagrams General Rules for neutral molecules which obey the “octet rule” 1 Determine number of outer level valence ele by Chiodos

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```									                   Practice Set on Writing Electron-Dot Formulas (Lewis Diagrams)

General Rules (for neutral molecules which obey the “octet rule”)
1. Determine number of outer-level (valence) electrons.
2. Determine reasonable “layout” of atoms, based on usual number of covalent bonds for each atom.
3. Place pairs of electrons between atoms, corresponding to the usual number of covalent bonds
(2e- = 1 bond — single, 4e- = 2 bonds — double, 6e- = 3 bonds —triple).
4. Place remaining electrons in non-bonded locations on those atoms which still lack an octet
5. Check results for:
a. correct number of bonds at each atom
b. complete octets
c. correct total number of valence electrons

Problems. Draw electron-dot diagrams for (answers on reverse):

A.   H2S

B.   CO2

C.   OCS

D.   N2

E.   C2H2

F.   C2H4

G.   C2H6

H.   PCl3
H

I.   CH3OH =         H    C    O

H        H

J.   H2CO

K.   N2H4

L.   C2Cl4

H        O

M.   CH3CO2H =       H    C    C

H        O   H
Lewis Diagram                         Valence-electrons            No. Bonds
..
A.   H:S:                                 1 + 1 + 6 = 8e-          H =1 and S = 2
..
H
..              ..
B.   ..O :: C :: O .                      4 + 6 + 6 = 16e-         O = 2 and C = 4
.
..              ..
C.   ..O :: C :: S .                      4 + 6 + 6 = 16e-         O = 2, S = 2, C = 4
.
:: ::
D.   : N :::N :                           5 + 5 = 10e-             N = 3, each
:: ::
E.     H : C :::C :H                      1 + 4 + 4 + 1 = 10e-     H = 1, each; C = 4, each
::
::
H..        .. H
F.      .. C :: C..                       2x4 + 4x1 = 12e-         H = 1, each; C = 4, each
H       :: H
H H
.. ..
G.     H : C : C :H                       2x4 + 6x1 = 14e-         H = 1, each; C = 4, each
.. ..
H H

..        .. ..
H.   : Cl : P : Cl :                      5 + 3x7 = 26e-           P = 3 and Cl = 1, each
.. .. ..
:: ::
: Cl :
..:: ::
H
.. ..           4 + 4x1
I.    CH3OH =               H: C: O :            + 6 = 14e-        H = 1, each; C = 4; O = 2
.. ..
H   H
H.
.          ..
J.     .. C :: O..                        1 + 1 + 4 + 6 = 12e-     H = 1, each; C = 4; O = 2
H        ::
H
H
.. ..
K.      :N:N:                             4x1 + 2x5 = 14e-         H = 1, each; N = 3, each
.. ..
H     H
..            ..
: Cl.: :.Cl:
.         .
L.        ..C :: C .                      2x4 + 4x7 = 36e-         C = 4, each; Cl = 1, each
.
:Cl:
..     ::: Cl:
..
..
H       O:
.
.. ...
M.    CH3CO2H =            H: C : C.      4x1 + 2x4 + 2x6 = 24e-   H = 1, each; C = 4, each; O = 2,each
.. .
H : O: H
..

```
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