BONDING
VALENCE ELECTRONS
Highest energy electrons (outer shell)
 Only s and p block elements contain valence
electrons, so how many valence electrons
can there be?????
 Noble gas=most stable

 How
many electrons? 8
Octet Rule: 8 valence electron’s are most
stable.
 Elements will find the easiest route to get 8
electrons (either gain or lose electrons)

LEWIS DOT STRUCTURES

Lewis Dot Structures/ Structural Formulas

Write the atomic symbol; place the appropriate
number of dots around the element to show the
valence electrons.
 C,

K, Cl, Kr
Ionic Compounds
Write the elements that are bonding, place
appropriate number of valence dots, use an arrow to
show where the electrons get traded, end equation
with ions, one complete, one empty element
 Example: NaCl, CaBr2

LEWIS DOT STRUCTURES/COVALENT CMPD

Covalent Compounds

Lewis Dot: same concept as ionic, but electrons do not
transfer

Structural Formulas: place a line in between bonded
elements, these lines represent paired electrons, left
over dots are unpaired electrons.

Number of bonds:
 Single
bond: one line, one pair of electrons
 Double bond: two lines, two pairs of electrons
 Triple Bond: three lines, three pairs of electrons
LEWIS DOT STRUCTURES/COVALENT CMPD

Rules of writing Covalent Compounds:






Count valence electrons (add for negative charges, subtract for
positive charges)
write skeleton with single bonds already in place
Place remaining valence electrons around elements
make stable octet, increase bond number if needed
E.G.: CO2, N2, CH4
Exceptions:




H, Li
satisfied with 2 electrons
Boron family
satisfied with 6 electrons (metals)
P, S
more than 8 electrons is OK
When one element is satisfied, but partner is not, the satisfied
element with donate a pair of electrons to make another bond =
Coordinate Covalent Bonds
Solids, liquids, and gases
STATES OF MATTER
KINETIC-MOLECULAR THEORY



Particles are hard spheres with insignificant
volume, mostly empty space, no attractive or
repulsive forces
Particles in constant, rapid motion
All collisions are perfectly elastic
SOLIDS
Particles vibrate about fixed points
 Highly organized, dense, and incompressible
 Do NOT take shape of container

LIQUIDS

Particles are in motion and are free to slide
past one another
 Vibrate
and spin as they move
 Particles are attracted to each other through
intermolecular forces
 Holds shape of container
 Less dense than a solid
 Not
enough energy to escape as a gas
GASES

Particles are in constant motion
 Take
shape of container
 Less dense than solids or liquids
 Forces of attraction are weaker
Pressure
PHASE DIAGRAM
Temperature
TRIPLE POINT VIDEO

http://www.youtube.com/watch?v=BLRqpJN9z
eA
GRAPH OF PHASE CHANGE
Molecules
separating
into gas
formation
Temperature
Molecules
separating into
liquid formation
Boiling
Point
Melting
Point
Gas
Liquid
Solid
Time
BOND POLARITY
BOND POLARITY

Covalent bonds differ in how bonded atoms share
electrons


Non-polar covalent bond:


Electrons are being pulled by both nuclei
Bonds are pulled equally (usually between two like atoms)
H2
Polar Covalent Bonds:




Two different atoms bond and electrons are shared
unequally
More electronegative atoms will have the stronger electron
attraction, will acquire a slightly negative charge (Example)
Less electronegative atom will acquire a slightly positive
charge(Example)
Charges are represented by lower case delta  (the atoms
charges are less than +1 and -1) (Example)
DETERMINING POLAR MOLECULES
A
molecule is polar when the atoms do not share
electrons equally
 This creates a slightly positive charge on one end
and slightly negative charge on the other

Look for:
 Unshared
electrons on the central atom (called
lone pairs)
 Different atoms surrounding the central atom

Examples: NH3
 What
about H2O? CH2Cl2
Ionic, metallic, and network
OTHER TYPES OF BONDS
TYPES OF BONDS
Compound
Description of Bond
Functional Unit (drawing)
Elements Combined
Do They Follow the
Octet Rule?
Ionic
Transfer of electrons
Attraction between
(+) and (-) Charges
Metals lose
electrons
Non metals gain
electrons
Crystalline structure
Positive attracts to
negative (metal to
nonmetals)
Draw
Metals
(cations)
Non-metals
(anions)
Covalent
Sharing of e-
Metal
Metal ions that are
surrounded by freeflowing e-
No set structure, molecules Two or more
near one another
non-metals
Draw
bound
together
Positive nucleus
Two or more
surrounded by electrons
metals
Draw
Yes, nonmetals accepts
e- to complete
outer shell,
metals donate
e- to revert
back to
complete outer
shell
All but
Hydrogen
No octet, no
full energy
level
PROPERTIES OF BONDS
Bond
Strength of
bond
Strongest
Very stable
Covalent
Properties
Melting/Boiling Solubility
Brittle solid
High melting
point
Usually high
solubility
Good
conductors in
solution
Ionic
Covalent
Metal
Weak strong
Easiest to
break
Conductor of
electricity?
Solid, liquid,
and gas
states
Low melting
and boiling
point
Low to high
solubility
Poor to nonconductors
Not as strong Ductile and
as ionic,
malleable
stronger than Solid, except
covalent
mercury
Varied stability
Medium
melting point
Not soluble
Good
conductors of
electricity
(electrons flow
freely)
FORCES
FORCES BETWEEN MOLECULES

Intermolecular forces
 Attraction
between molecules
 Weaker than atom bonding
 Used to determine physical properties of the
molecule (such as state of the molecule solid,
liquid, or gas)

Strongest  Weak
Ionic bond  Hydrogen Bonds  dipole Interaction  Van der
Waals
Types of Forces
Van der
Waals/London
Dispersion
Dipole-dipole
Hydrogen bonds
Mimic ionic compounds
(attracted by charges,
but weaker)
Strongest (includes all
3 forces)
Strength
Increase strength of
forces as electron
number increases
Types of
Molecules
Any covalent
compound with
electrons (non-polar)
A force between 2 polar
molecules
Force between 2 very
polar, hydrogen
containing molecules
Description
of force
More
electrons=stronger
the force
Positive atom on one
molecule attracts the
negative atom of
another molecule
Created with O, F, & N
ONLY
Examples
Diatomic elements:
Br I N Cl H O F
CH3COCH3
H2O where H of one
water is attracted to
the O of another water
FORCES AND PROPERTIES
Physical properties depend on type of bond (ionic
or covalent)
 The variety in covalent compounds are due to
intermolecular forces
 Properties

Melting point: only the weak attractions need to be
broken.
 Boiling Point: break apart molecules of liquid
 Solubility: stronger the intermolecular force the harder
it is to be soluble.

QUESTIONS

Define the following:
 Boiling
point
 Melting point
 Evaporation
How do each of the above relate to the type of
bond in a molecule?
 What role does intermolecular forces play in the
strength of bonds?
 Draw Isopropyl Alcohol ((CH3)2CHOH), methanol
(CH3OH), acetone (CH3COCH3), and water.
 What type of forces are present in each?
