Warm Up: December 10

1
Warm Up December 10

• Distinguish between the Bohr model and the
  quantum mechanical model of the atom.
• 2. Carbon-14 is a radioactive isotope that
  decays by releasing a beta particle. Write the
  nuclear equation that represents this decay.

2
Molecular Geometry and VSEPR Theory

• Whenever the atoms of a molecule bond together,
  the molecule takes on a particular shape.
• Molecular geometry refers to the
  three-dimensional arrangement of a molecules
  atoms in space.
• VSEPR theory is the model used to explain the
  shapes of molecules.

3

• VSEPR Valence Shell Electron Pair Repulsion
  Theory.
• The main idea of this theory is that electron
  pairs on the central atom of a molecule will
  position themselves in such a way as to minimize
  repulsion.
• There are two types of electron pairs 
• bonding pairs (shared)
• nonbonding pairs (unshared )

4

• Example CH4
• 4 electron pairs
• 4 bonding / 0 nonbonding pairs
• molecular geometry tetrahedral
• Example NH3
• 4 electrons pairs
• 3 bonding / 1 nonbonding
• molecular geometry trigonal pyramidal

5

• Example H2O
• 4 electron pairs
• 2 bonding / 2 nonbonding
• molecular geometry bent

6
VSEPR and Multiple Covalent Bonds

• For the VSEPR model, multiple bonds are counted
  as one bonding pair when determining the shape of
  the molecule.
• Example CH2O
• 3 electron pairs
• 3 bonding / 0 nonbonding
• molecular geometry trigonal planar

7

• Example NOCl
• 3 electron pairs
• 2 bonding / 1 nonbonding
• molecular geometry bent
• Example CO2
• 2 electron pairs
• 2 bonding / 0 nonbonding
• molecular geometry linear

8
Bonding Pairs Nonbonding Pairs Shape Example
2 0 Linear CO2
3 0 Trigonal Planar CH2O
2 1 Bent NOCl
4 0 Tetrahedral CH4
3 1 Trigonal Pyramidal NH3
2 2 Bent H2O
9
Its Your Turn!

• Predict the shape of the following molecules.
• PBr3
• TeF2
• SiO2

10
Outcome Sentences

• After reflecting on todays lesson, complete
  three of the sentence starters in your chemistry
  journal entry for today.

• Sentence Starters
• Ive learned
• I was surprised
• Im beginning to wonder
• I would conclude
• I now realize that