1. Part 1: Molecular Orbitals
Bonding Theories
Part 1: Molecular Orbitals

2. Objectives
Describe the relationship between atomic and molecular orbitals

3. Important Vocabulary Molecular orbitals Bonding orbital Sigma bond
Pi bond

4. Molecular Orbitals
The model for covalent bonding you have been using assumes that the orbitals are those of the individual atoms
There is a ____________________of bonding that describes the electrons in molecules using orbitals that exist only for groupings of atoms
______________form when two atoms combine and their atomic orbitals overlap

5. Forming Molecular Orbitals
Just as an atomic orbital belongs to a particular atom, a molecular orbital belongs to a molecule as a whole
____________ are required to fill a molecular orbital just like an atomic orbital
A molecular orbital that can be occupied by 2 electrons of a covalent bond is called a bonding orbital

6. Formation of Molecular Orbitals

7. Sigma Bonds
When two _____ orbitals combine to form a _______ orbital that is _______around the axis connecting two atomic nuclei, a _________ is formed
The symbol for this bond is the Greek letter sigma (σ)

8. Repulsion Forces
In general, covalent bonding results from an ________ between the _______ and _________ of the nuclei and electrons involved
Because their charges have the same sign, nuclei repel other nuclei and electrons repel other electrons

9. Sigma Bonds with p orbitals
Atomic p orbitals can also overlap to form molecular orbitals
They overlap _____________

10. Pi Bonds In some molecules, orbitals can overlap side-by-side.
This side-by-side overlap of atomic p orbitals produces a ______________________
When a pi molecular orbital is filled with 2 electrons, a pi bond results
In a pi bond, the bonding electrons are most likely to be found in sausage-shaped regions above and below the bond axis of the bonded atoms
It is represented by the ______________
It is _______________ around the bond axis , the pi orbitals bonding overlaps less than sigma bond
Thus, pi bonds are ___________ than sigma bonds

11. Pi Bonds

12. Why are pi bonds weaker than sigma bonds?

13. Determining Molecular Shapes
Three-dimensional shape is important in determining the molecule’s physical and chemical properties
For example:

14. Lewis Structures & Molecular Shape
A molecule made of only two atoms has a _____ shape only
Molecules with more than two molecules are not as easy to determine
Chemists must use a model to predict the shape of these molecules
This model is based on ______________________________