What happens if interacting
things do not want to give?
They must share…
What does it mean to share an e- ?
– shared e- “belongs” to both atoms
– both complete octets
– valence energy levels of overlap
Linked
Linked
• the sharing/overlap binds the atoms together
and is called a covalent bond
Pg 242
Write
in the
box
Ionic vs. Covalent
Bond
How are these
• Nonmetals share
e- forming overlapping valences that
diagrams
keep atomsdifferent?
together
– Overlap forms a new shape=molecule
• Metals give e-; Nonmetals take e-; electrostatic
attraction created keeps atoms together
– Ions “stick” together = formula unit
Drawing Bonding
Venn diagram model
Draw Lewis symbol for Cl
Is one Cl noble gas stable?
Pg 243-246
Lewis Structure
show shared pair(s)
as line and
unshared pairs as
dots
single line = “single bond”
What about water???
Draw Lewis symbols for each atom of water
then match up the electrons to make bonds!
Venn diagram
Draw its Lewis
structure
Pg 252-255
overlap creates a
new molecule
with its own
shape
Try N bonding with H
• Draw Lewis symbol for N & H
• How will they share electron pairs???
• Draw Lewis structure
for new molecule.
Pg 252-255
Try matching up carbon with
hydrogen…
Drawing Lewis Structures Pg 252-255
“step by step” example…PCl3
1.
2.
3.
4.
5.
6.
Sum valence electrons for all atoms
Divide total # of ve- by 2 to give # of electron pairs
Determine which atom is the CENTRAL atom???
Surround the central atom with 4 electron pairs
Put the other atoms around the central atom
Use the remaining pairs to complete octets around
each remaining atom
7. If there are not enough electron pairs to provide an
octet for each atom, move nonbonding electron pairs
between 2 atoms that already share a pair
PCl3 is used to make numerous
phosphate compounds for industrial
purposes one of which is PSCl3
 which is then used to make
parathion which is used as an
insecticide
Lewis Structure Practice
Cl2
NF3
HF
CHCl3
(C is central)
Ions have a charge. How will this change your
total # of valence electrons???
sulfate ion
chlorate ion
Equivalent Resonance Structures
Draw Lewis Structure for:
SO3
Pg 256-258
VESPR
Pg 259-262
Valence Electron Shell-Pair Repulsion
• Electron domain – region about a central
atom in which electrons are likely to be
found ((bonding AND nonbonding))
• Bonding electrons – electrons shared
between atoms
• Nonbonding electrons (lone pairs) –
electrons that are not shared but are
needed to complete atoms octet
VESPR
Pg 259-262
• Electron domains (lone pairs and bonds)
will orient naturally to “try to get out of
each other’s way”
Linked
• The best arrangement of a given number
of electron domains is the one that
minimizes the repulsion among them
• 3-d shape depends on the bond angles
resulting from domain arrangement
1) draw each Lewis structure
2) determine the # of electron domains around the
CENTRAL ATOM
3) how many electron domains are bonding sites?
H2O
CH4
NH3
4 electron domains = electron domain
geometry is tetrahedral BUT with
4 bonds
3 bonds
2 bonds
the molecular geometry is
Tetrahedral
Trigonal
Pyramidal
Bent
When sharing, why would one interacting
thing get more than another???
Electronegativity - ability of an atom in a
molecule to attract electrons to itself (electron affinity)
Pg 263-264
Linked
Pg 263-264
Polarity
Linked
•Polar (“puller”) – atoms pull electrons differently;
results in uneven distribution
–Gives bond partial positive and partial
negative “dipoles”
• Nonpolar – atoms pull electrons equally; results
in even distribution
How “puller” is polar?
use electronegativity
values to determine the
extent of the polarity
non-puller
polar bear
to be “puller” difference
MUST be greater than 0.4
Example: Determine
extent of polarity of
a B – Cl bond
puller polar bear
Pg 263-264
Dipole Moments
• Which of the following bonds is the most
polar? Which one is Non-polar?
Cl – Cl
H–O
C–O
Br – F
N–H
C–H
Molecular Polarity
Pg 265
Dipole moment of multi-atom molecules
depends on BOTH polarities of individual
bonds and molecular geometry
Molecular Polarity
polar
polar
non-polar
non-polar
polar
Polarity results in ….
Intermolecular Attraction
Pg 265
Dipole-Dipole of one molecule attracts
to the
of another
Ion – Dipole attraction
Pg 265
Attraction of ionic charge and partial dipole charge of a polar
molecule
How do compounds dissolve???
ion–dipole attraction separates
NaCl formula units into
isolated ions
Linked
dipole-dipole attraction cause
water molecules to surround
and isolate sugar molecules
Naming Binary Molecular
Pg 248-249
Compounds
• element furthest to the left on table should be
written first
• if same group element with higher atomic #
should be written first
• second element name should end with “ide”
• Greek prefixes designate # of atoms of each
element
((prefix mono is NOT used for first element)))
Pg 248-249
Prefixes
1 mono
4 tetra
7 hepta
10 deca
2 di
5 penta
8 octa
3 tri
6 hexa
9 nona
SO…
CO
SF6
N 2O
P2O3
Practice
• Cl2O3
BrF3
• I2O4
SO3
•
•
•
•
dihydrogen monosulfide
Iodine monobromide
Nitrogen monoxide
Chlorine dioxide