Unit 5: Soap
Section 5.4- 5.6 Guided Notes
Section 5.4: Polarity of Molecules
Electronegativity is the pull that an atom has for ________it shares with another atom in a bond.
It as a periodic trend can be noted on the following periodic table of electronegativity values. (Deters, K.,
The Chemistry that You Need to Know).
As you move from left to right across a period, notice that the electronegativity values increase with
Fluorine having the greatest value of 4.0. As you move down a group from top to bottom, the values
decrease.
Covalent Bonds
Covalent bonds results when electrons are ___________between two non-metal atoms. The “sharing”
can be uneven (polar) or even (non-polar).
Polar Bonds
 Polar covalent bond: a ________separation of charge
 One atom pulls the electrons closer to itself and has a partial __________charge.
 The atom with electrons farther away has a partial ____________charge.
Non-Polar bonds:
 Non polar covalent bond: atoms pull ____________on the shared electrons. The
electrons are not closer to one atom than another. There is no separation of charge.
Unit 5: Soap
Section 5.4- 5.6 Guided Notes
Draw an example of N 2 showing two atoms sharing electrons equally.
Electronegativity value for Nitrogen = 3.0. Each atom has a value of 3.0. The difference in these values
is zero. Therefore, the atoms pull evenly on the electrons. This is a Non-polar covalent bond.
Draw an molecule of CH 4 where atoms are sharing electrons almost equally:
Electronegativity values: Carbon = 2.5 Hydrogen = 2.1 The difference in electronegativiy is 0.4
therefore the carbon pulls on the electrons slightly more, pulling them towards the carbon atom. The
difference is not enough to create a polar bond. This is a non-polar covalent bond.
Draw a molecule of CH 2 O that shows uneven sharing of electrons.
Electronegativity values: Hydrogen= 2.1 Carbon = 2.5 Oxygen = 3.5
The carbon-hydrogen difference is only 0.4 which is not strong enough to create partial charges. The
oxygen atom because of its higher EN value pulls significantly harder on the electrons than the carbon
does. This creates a polar covalent bond with an EN difference of 1.0.
Showing partial charges (polarity):
 Use δ for “partial” with a + or – to indicate the partial negative end and partial
positive end.
 Use an arrow pointing towards the partial negative atom with a “plus” tail at the
partial positive atom
 These are referred to as dipoles.
Draw example using the molecule of CH2O from above.
Ionic Bonds
 Ionic bonds occur when the electronegativities of two atoms are so
_________________that they can’t share electrons evenly or unevenly. One atom just
takes the electron from the other.
 Ionic bonds form between a __________ atom and a ___________ atom.
 Electrons are transferred from the metal to the non-metal.
Unit 5: Soap
Section 5.4- 5.6 Guided Notes
Determining bond type using Electronegativity difference (ΔEN)
 Find the EN value for each atom in the bond.
 Find the absolute value of the difference in their values. (subtract the values)
 Use the following ranges to determine bond type:
Difference in Electronegativity (ΔEN)
0.4 or less
Greater than 0.4 but less than 1.4
Greater than 1.4
Bond Type
Non-polar covalent bond (NPC)
Polar covalent bond
(PC)
Ionic bond
(I)
Polar Bonds versus Polar Molecules
 Not every molecule that has a ____________bond is polar itself. If the polar bonds
cancel out, then the molecule is overall ________________.
The polar bonds cancel out.
The polar bonds do not cancel out.
No net dipole
Net dipole
Practice: If the bond is polar, draw the polarity arrow:
C-H
O-Cl
F-F
C-Cl
Unit 5: Soap
Section 5.4- 5.6 Guided Notes
Valence Shell Electron Pair Repulsion (VSEPR)
 You must think about molecules in 3-D to determine if it is overall polar or non-polar.
Because electron pairs that are not part of bonds _____ each other, the electrons will
move apart to be as far away as possible. This repulsion sometimes creates forces on
the bond which causes the bonds to bend creating molecules that have different
shapes.
Molecular Geometry
linear
tetrahedron
Trigonal planar
bent
Trigonal pyramidal

© 2009 Kendall/Hunt Chemistry
Discovering Chemistry You Need to Know
Unit 5: Soap
Section 5.4- 5.6 Guided Notes
Molecular Geometry
octahedron
bent
Trigonal bipyramidal
© 2009 Kendall/Hunt Chemistry
Discovering Chemistry You Need to Know
Let’s Practice:
Draw the molecule for ammonia, NH3. Is it polar or non-polar? What shape is it?
Draw the molecule for water, H2O. Is it polar or non-polar? What shape is it?
Draw the molecule for carbon tetrachloride, CCl4. Is it polar or non-polar? What shape is it?
________________________________________________________________________________
Section 5.5 : Intermolecular Forces (IMF)
Intra-molecular forces versus inter-molecular forces-----THERE IS A DIFFERENCE!!!!!
Intramolecular forces are forces _____________the molecule (in the chemical bonds).
Unit 5: Soap
Section 5.4- 5.6 Guided Notes
 Breaking intramolecular forces within the molecule is a ___________ _________.
Bonds are broken and new bonds form to make new molecules.
Intermolecular forces are forces that occur ________________separate molecules.
 Breaking of intermolecular forces (between separate molecules) is a ________
__________.
 Example: breaking glass is breaking the intermolecular connections between the glass
molecules to separate it into pieces
 Boiling water is breaking the intermolecular forces in liquid water to allow molecules to
separate and be individual gas molecules.
Types of Intermolecular Forces
London dispersion forces
 Occurs in polar molecules
 “electrons” momentarily move toward one side (or gang up on one side)
 A partial ________________of charges is created and the molecule is _____________
polar
 The ______________area of one temporarily polar molecule can be attracted to the
negative of another molecule.
Draw a diagram:
 London Dispersion (LDF) are the weakest of the intermolecular forces because
molecules can’t form all the time. Larger molecules have
_______________________London Dispersion forces than smaller molecules.
Dipole-Dipole Forces
 Polar molecules have permanent partial separation of charge called a _____________.
 The positive area of one molecule can be attracted to the ________________area of
another.
 The partial positive and partial negative “poles” are shown in a diagram as
________________.
 Dipole-dipole forces are _______________than London dispersion forces.
Draw a diagram:
Unit 5: Soap
Section 5.4- 5.6 Guided Notes
Dipole-dipole forces are stronger than LDF.
Hydrogen Bonding
 Hydrogen has only 1 proton and 1 electron. It bonds using the only electron.
 When the only electron hydrogen has is shared UNEVENLY (a polar bond) with another
atom, the electron is farther from the hydrogen ________________.
 This happens when hydrogen bonds with __________, _______________, and
_____________.
 A very strong ________________forms because there are no other electrons around the
hydrogen to counter-act the proton’s positive charge.
Draw a diagram:
Hydrogen bonding is the strongest of all the intermolecular forces.
YOU TRY: Put the following forces of attraction in order from weakest to strongest: ionic bond, covalent
bond, hydrogen bonding, London dispersion forces, dipole-dipole forces,
_____________________________________________________________________________________
Section 5.6: Intermolecular Forces and Properties
 The number and ____________________of IMF affects the properties of the
substances.
 ______________is required to break IMF’s.
 Energy is ______________when new IMF’s are formed.
IMF and Changes in State (melting, boiling, etc. )




From solid to liquid: some IMF’s are broken
From liquid to gas: the remainder of IMF’s are broken
This requires energy.
The ______________the IMF the more energy required to melt, boil, or evaporate.
Stronger IMF = higher melting and boiling point.
A Word or Two about Water
 Water is a small molecule and generally speaking smaller molecules have low melting
and boiling points. Water is an exception to this statement.
Unit 5: Soap
Section 5.4- 5.6 Guided Notes
 Water is polar and can form ________________interactions and __________bonding.
Its melting point is much higher as a result.
Viscosity
 ________________--to flow
 Molasses is more viscous than water.
 _______________-molecules and molecules with high IMF’s “stick” together more.
More sticking together = higher viscosity.
Solubility
 Solute: _____________________________________
 Solvent: ____________________________________
 In order for something to be dissolved, the IMF’s must be broken within the solute and
solvent. New IMF’s must be formed.
 Dissolving process:
o Water breaks some IMF with other molecules to allow them to spread out.
o New IMF begin to form with solute molecules
o As these new IMF’s form, the solvent “carries off” the solute
 “like dissolves like”: polar solvents dissolve polar solutes; non-polar solvents dissolve
non-polar solutes
 Example: oil and water: water is polar. Oil is non-polar. Oil will not dissolve in water.
Surface Tension
 Surface tension:
 Due to _________________-IMF’s.
 Higher IMF = higher surface tension.
Soap and Water
 Soap has a _________________-head and a ______________tail.
 The polar part interacts with _________________. The non-polar part interacts
with _________________________.
 The soap surrounds the “dirt” and the outside of the micelle interacts with
__________.
 The soap disturbs the water molecules ability to _______________to form IMF’s.
 Soap lowers ______________ ________________ of water to allow the water to
spread over dirty dishes.