How are Molecules
Depicted?
6.2
Lewis Structures
Valence e- = an e- in the outermost
E level of an atom and determines
the chemical properties
Lewis Structure = a structure in
which e- are represented by dots:
dot pairs or dashes b/t 2 atomic
symbols represents pairs in
covalent bonds
Lewis Structure
Single Bond = covalent bond in
which one pair of e-’s are shared
b/t 2 atoms
Unshared pairs = a nonbonding
pair of valence e- not involved in
bonding to another atom
Simple Lewis Structures
Draw the Lewis structures for the
following elements…
K, Sr, Al, Kr, P, O
Remember e- want to be as far
apart as possible
How to draw LS for more complex
molecules
1. Draw the LS for each element
2. Put least electronegative
element in center
3. Arrange other elements around
central atom to satisfy octet (H
only needs 2)
4. Change dots to lines to show
bonds b/t atoms
Practice
Try drawing the Lewis structures
for…
NH3 CH4
H2O
CH2F2
Worksheet on Lewis Structures!
F2
O2
N2
C2H4
Multiple Bonds
Used when single bonds don’t
satisfy octets for each atom
Resonance structure – a
possible Lewis structure of a
molecule when more than 1 L.S.
is possible
Delocalized – e- shared b/t more
than 2 atoms
Practice
Ca
KBr
CO2
HCN
Lewis Structures with Ions!
NH4+
CNCO32OH-
Naming Covalent Compounds
Inorganic molecular compounds
Specify # of each type of atom
P4O6 – Tetraphosphorus hexoxide
P4O10 – Tetraphosphorus decoxide
C
o
v
a
l
e
n
t
p
r
e
f
i
x
e
s
Mono
Di
Tri
Tetra
Penta
Hexa
Hepta
Octa
Nona
Deca
1
2
3
4
5
6
7
8
9
10
Naming Covalent Compounds
If there is 1 of the first element,
mono is omitted from the word
CO – carbon monoxide
CO2 – carbon dioxide
Naming Covalent Compounds
1st element – named 1st – usually
least e-neg
2nd element – named 2nd – usually
most e-neg – add ide ending
Drop vowels o and a from prefix
before adding it to a root that
starts with a vowel
Naming Covalent Compounds
N2O4 – Dinitrogen tetroxide
SF6 – Sulfur hexafluoride
Some common names are used
instead of technical name
H2O – water – not dihydrogen
monoxide