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M2 Molecule-Shapes-Student-Handout for exam 1 and 2
General Chemistry I (CHE 115)
Concordia University Saint Paul
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Molecule Shapes
MODEL 1:
Molecule Shapes Simulation
(phet/en/simulation/molecule-shapes)
PART I: ELECTRON DOMAINS
- Explore the Model screen of the simulation. As you explore, answer the following questions.
a. How does adding an atom affect the position of existing atoms or lone pairs? As the atoms get closer together, the bond angle keeps decreasing.
b. How does adding a lone pair affect the position of existing atoms and lone pairs?
Same as adding an atom.
Is the effect of adding bonded atoms and lone pairs to the central atom similar? Explain why this could be the case. Correct. Both types of domain take up the space. They repeal other electron domain.
How do the electrons in bonds (bonding domains) differ from lone pairs (non-bonding domains)?
Electrons in bonds are shared between 2 atoms. Electrons in lone pairs only belong to 1 atom.
MOLECULE SHAPES 1
We can think of a bond or a lone pair of electrons as a “domain” of electrons. Single bonds, double bonds, and triple bonds each count as one domain.
- What happens to the bond angle when you add or remove an electron domain?
The bond angle decreases.
- Can you force the atoms into new configurations by pushing atoms around? What does this suggest about the configuration of atoms in real molecules?
Yes, you can, but it won’t stay in a different configuration, it will adopt the lowest energy geometry. The configuration of atoms in real molecules is flexible.
- What is the difference between Electron Geometry and Molecule Geometry?
Electron Geometry accounts to all domains; Molecule Geometry only accounts for bonding domains.
- In one or two grammatically correct sentences, write a definition for the term Molecule Geometry. Molecular geometry is a term in chemistry used to describe the shape of the molecule. It is the arrangements of atoms in relation to a central atom in a three-dimensional space.
3 ○ Trigonal planar 120º
4
○
Tetrahedral 109º
In the Model screen, build a molecule with 5 atoms attached to the central atom. Look at the molecule geometry and electron geometry. Predict what will happen to the molecule geometry as you replace atoms with lone pairs.
In the following table draw the molecule geometry. As a group, make a prediction for each first, and then compare your answers with the simulation.
Predict First, Then Compare with the Simulation
Number of Domains Around Central Atom
1 Lone Pair 2 Lone Pairs 3 Lone Pairs 4 Lone Pairs
3
4
Your Prediction:
Five atoms would give us EG and MG of Trigonal Bipyramidal.
Aft laci ith lo ai it i EG S idal d MG O tahed al.
4
PART 3: COMPARING MODEL VS. REAL MOLECULES
- Explore the Real Molecules screen.
a. List the molecules that show a difference in bond angle between “Real” and “Model”. Note: differences in bond angle may be small.
Molecule Number of Lone Pair Domains
H2O 2
CIF3 2
SO2 1
NH3 1
SF4 1
BrF5 1
b. What do all of the molecules in the table have in common? All of them have at least one lone pair
c. What trend do you observe that distinguishes lone pairs from bonding domains? More space is taken
M2 Molecule-Shapes-Student-Handout for exam 1 and 2
Course: General Chemistry I (CHE 115)
University: Concordia University Saint Paul
