Post on 23-Jun-2015
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BELLWORK- Determine ShapeDraw the Lewis Dot Structure and the 3D structure for ethane (C2H6) and ethene (C2H4). Do these molecules have any polar bonds?
In reviewEqual sharing of electrons = covalent
LOW electronegativity difference
Unequal sharing of electrons = polar
MEDIUM electronegativity difference
Transfer of electrons = ionic
HIGH electronegativity difference
2 bonding domains
Three bonding domains
Four bonding domains
Three bonding and one lone pair
Two bonding and two lone
pairs
Bond polarity and molecule shape determine if a molecule is polar
Bond polarity --- When a bond has a partial negative charge on one atom and a partial positive charge on the other atom.
Molecule shape--- the arrangement of atoms in three dimensions (3-D)
A polar molecule has polar bonds and asymmetry
A polar molecule has polar bonds and asymmetry
Polar bonds Non-polar molecule
Symmetry- all sides are the same
δ-
δ-
δ-
δ-δ+
A polar molecule has polar bonds and asymmetry
Polar bonds Non-polar molecule
Symmetry- all sides are the same
Polar bonds Polar molecule
Asymmetry- has different sides
δ-
δ-
δ-
δ-
δ-
δ+δ+
negative side
Positive side
If the electrons are not distributed equally, the
molecule is polar.
The molecule has a negative
end and a positive end.
A polar molecule has a partially positive side and a partially negative side.
The arrow labels the molecular polarity.
It shows that electrons are mostly by the oxygen atom
OH H
Polar molecules are affected by electric fields
Polar molecules have two poles; one is partially positive and one is
slightly negative.
Positive end
Negative end
N
HHH
The positive pole (+) is attracted to
negative ions
and
the negative poles(-) in other polar molecules.
POLAR MOLECULES INTERACT!!
+
POLAR MOLECULES INTERACT!!
The negative pole (-) is attracted to
positive ions
and
the positive poles(+) in other polar molecules.
Water is a molecule that has two polar O-H bonds.
The electrons are not distributed evenly, so the water molecule is polar.
The negative pole is at the oxygen.
O is more electronegative than H, so electrons are
pulled toward O.
Also, there are two lone pairs around oxygen.
negative end
positive end
Na+(aq)
A dissolved sodium ion
Water is very good at dissolving salts because it can surround anions & cations.
Practice- Using last night’s homework assignment, label the molecular polarity
on the four pictures
H F
For the rest of the period work on your molecular modeling lab•Find a molecule that contains polar bonds•Build the molecule using a molecular modeling kit•Draw a sketch of the molecule
•Label the bond polarity using δ+ and δ- •Label the molecular polarity using
HW- complete bonding practice problems #1-#17
Tuesday = cover network solids and intermolecular forces. HW- Section 8.4
Block Day = Complete modeling lab, plus finish
bonding practice problems. Friday = Chapter Eight QUIZ!!
Practice- Draw the 3D structures for these molecules and label the bond polarity and the molecule polarity.
1. H2O
2. CH4
3. CH3F
4. CH3CH3
5. CH3CH2OH
6. NH3
7. CO2
8. CH2CH2
9. HCN
10.
11.