Post on 29-May-2020
transcript
Agenda
• HW:
• Simulation: Bonding Simulation (PBS and ACT) Part 2 Covalent Bonding
Compounds
• EXP Drawing Covalent Molecules
• Read Ch 7, 8, 9 and PP7, 8, and 9Note: exclude Hybrid Orbitals
• Unit 4 Exam (Bonding) March 10, 2020
NOTE: NO assessment on Hybrid
orbitals, properties, and IMF/s
• ICA:
• Quiz: Nomenclature 2 - 5
• EXP Drawing Covalent
Molecules(One Note: Content Library: Unit 4: Topic 2c:
EXP)
• Pilot: Pearson • PhET Simulations
• EXP Properties Lab
• Virtual Lab
Learning Goals II
Topics• Molecules: Nonmetals and Nonmetals
elements/compounds; Polar or Nonpolar
• Use Electronegative Values (Polar vs. Nonpolar)
• Covalent - Polar vs. Nonpolar Bonds
• Molecules – Polar vs. Nonpolar Molecules
• Properties of Ionic vs. Covalent vs. Metallic (vs. network solids) (p. 244)
• Bond Dissociation Energy
• Intermolecular Forces (IMF)
Additional Tools/Skills• VSEPR (p. 232)
• Diatomic Elements (p. 222)
• Polyatomic Ions (p. 257)
• Bond Types (p. 238)
• Polar Molecules (p. 238)
• Reference Packet
Problem Pools
Chapter Questions Standardized Test Prep
7 4, 7, 8, 10, 12, 19, 22, 25, 27, 31, 35, 37, 40, 41, 42, 51, 53, 65,
78, 79***Exclude ionic/metallic crystalline structures. Just enjoy the beauty of the structures
and understand general concept of + and – attractions.
STP all
*** same notes
8 3, 4, 5, 11, 16, 18, 21, 22, 30, 31, 36, 37, 40, 41, 45, 48, 50, 52,
54, 58, 59, 60,
61, 63, 68, 69, 74
STP all
9 43, 44, 45, 46, 51, 53, 57, 58, 60, 65, 68, 70, 81, 83, 84 STP all
Suggested problems from the textbook "Chemistry" (Prentice Hall). These are only from the Assessment and Standardized Test Prep found at the end of the chapters. There are also questions available at the end of each section (in the textbook) for more practice.
Additional Resource: Pearson
EasyBridgehttps://launchpad.classlink.com/Issaquah
Activity:
Bonding Simulations
Part 2 Covalent Bonding
ACS:
https://teachchemistry.org/classroom-resources/ionic-covalent-bonding-simulation
PBS:
https://kcts9.pbslearningmedia.org/resource/lsps07.sci.phys.matter.ionicbonding/ionic-
bonding/
https://kcts9.pbslearningmedia.org/resource/lsps07.sci.phys.matter.covalentbond/covalent-
bonding/
Learning Goal
WHY do certain substances have high melting point or are more soluble in water, or can conduct electricity....WHY?
because
Molecular Geometry determines Bond Polarity which determines Molecular Polarity which
determines Attraction which determines Properties
HOW: Therefore, we will learn how to know if a molecule is attractive (polar) or sometimes attractive (nonpolar).
How To: Identify the Molecular Geometry
• Step 1: Just know how the atoms attach.
• Diatomic molecules are always linear.
• The central atom must be able to make more than 1 bond. Thus, can never be Hydrogen or a Halogen.
• Always show ALL unshared (lone pairs) in a molecule.
• Use a line to represent shared pairs.
• Step 2: Use AXE system to identify the molecular geometry.
• VSEPR
• Unshared Pairs of Electrons take up more space than shared electrons.
• Molecular Geometry vs. Electron Geometry
Step 1: Just know how the atoms attach.
• Step A: Count up the total valence electrons in the molecule.
• Step B: Set up the atoms using single bonds. (1 line = 1 bond = 2 electrons)
• Step C: Use the duet/octet rule to make each atom “happy” (aka. Stable)
• Lone pairs of electrons should be included.
• Step D: Recount all the electrons in the molecule and it should equal the total valence electrons identified in Step A.
• Step E: If there are too many electrons in the Lewis Structure, remove all unshared electrons and add a double (or triple) bond and start with Step C again.
HONC Rule
This generally works for these elements.
However, there are always exceptions. For example, Oxygen can form a Triple Bond with Carbon.
Also, Sulfur and Phosphorus and Boron are exceptions to the Octet Rule and thus have either less or more bonds than expected.
NOTE: How do you know which atom is the central atom??? Use the HONC rule. Should be an atom that can form at least 2 or more bonds.
Step 2: Use AXE system to identify the molecular geometry.
• A Central Atom
• X (or B) Other Atoms
• E Unshared Electron Pairs on the CENTRAL atom
• Note: At this point the presence or absence of lone pairs on
the central atom is what affects the molecular shape.
VSEPR
A Central Atom
X (or B) Other Atoms
E Unshared Electron Pairs
https://i0.wp.com/www.compoundchem.c
om/wp-content/uploads/2014/11/VSEPR-
Shapes-of-Molecules.png?ssl=1
Molecular Geometry
•Molecular Geometry
•Lone pairs/ Nonbonding electrons/ unshared pairs**
•Electronegativity
•Dipole moment
•Polar vs. Nonpolar bonds
•Polar vs. Nonpolar molecules
VSEPR
https://i0.wp.com/www.compoundc
hem.com/wp-
content/uploads/2014/11/VSEPR-Shapes-of-Molecules.png?ssl=1
Resource: Compound Interest
Experience 3:
Covalent bonds
Read the pages on Molecular
Geometry and answer the CCC
question in the eText or the class
copy.
Handout: Calculate Bond Polarity
Resource: PhET Simulation
"Molecule Shape"
PhET: Molecule Shapes
Use the PhET Simulation to see the molecule in 3-D. This is great when you compare NH3 and BF3. You can actually see that BF3 is planar.
Their shapes are determined by all the lone (nonbonding) and bonding electron pairs around the central atom.
PhET: Molecule Shapes
This will show up on the PhET.
However, you will only be asked about the Molecular Geometry.
PhET: Molecule Shapes
This will show up on the PhET.
However, you will only be asked about the Molecular Geometry.
Electron Geometry Molecular Geometry
Where are the
electrons?
To determine if the bond
and, ultimately the molecule, is
polar, we need to know where the
electrons are more likely to be
found.
Polar Bond
Dipole moments occur when there
is a separation of charge.
They can occur between two ions in
an ionic bond or between atoms in a
covalent bond
Dipole moments arise from
differences in electronegativity. The
larger the difference in
electronegativity, the larger
the dipole moment.
Activity:
Building Molecules
1. Build two diatomic molecules (nonpolar and polar) and two polyatomic molecules (nonpolar and
polar).
2. Take a photo of the diatomic molecules together and the polyatomic molecules together.
3. Label the images with the following:
Chemical Symbols
Electronegativity Values
Dipole moments on Bonds
Use the d- and d+ symbols
Overall Dipole moment
4. Caption the images with the names of the molecules and their overall polarity.
Do you now understand
this image about
Molecules?
Polar vs. Nonpolar
Make sure you also know how to
draw or interpret Bohr models as
well as Lewis Dot Structures.
PhET: Molecular Polarity
• Predict how changing electronegativity will affect the bond polarity.
• Explain the relationship between the bond dipoles and the molecular dipole.
• Determine if a non-polar molecule can contain polar bonds.
• Describe how the ABC bond angle effects the molecular dipole.
• Compare the behavior of non-polar and polar molecules in an external electric field.
PE Diagram: Bond
Formation
If the hydrogen atoms are too far
apart, attractions are weak and no
bonding occurs. If the atoms are
too close, strong repulsions occur.
The minimum potential energy
occurs at an optimal distance
between the nuclei. This distance is
the bond length.