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.

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 molecule’s atoms in space. VSEPR theory is the model used to explain the shapes of molecules.

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 )

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

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

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

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

Bonding Pairs Nonbonding Pairs Shape Example 2 Linear CO2 3 Trigonal Planar CH2O 1 Bent NOCl 4 Tetrahedral CH4 Trigonal Pyramidal NH3 H2O

Its Your Turn! Predict the shape of the following molecules. PBr3 TeF2 SiO2

Outcome Sentences Sentence Starters After reflecting on today’s lesson, complete three of the sentence starters in your chemistry journal entry for today. Sentence Starters I’ve learned… I was surprised… I’m beginning to wonder… I would conclude… I now realize that… 10