1. When electrons are shared between 2 atoms, the atomic orbitals of these 2 atoms
can overlap in 2 different ways, forming either sigma or pi bonds.
Sigma Bond – a bonding orbital, consisting of a single lobe where the electron
density is concentrated in the region directly between the 2 bonded atoms
(or on the bond axis). This is the stronger of the 2 bonds.

2. The other way for orbitals to overlap and form bonding orbitals is called :
Pi Bonds – made from unhybridized electron pair, found in multiple
bonds, consists of 2 lobes, 1 above the bond axis and 1 below the bond axis.
(along the axis the electron density is zero). These bonds are weaker than
sigma bonds.
Use these rules to determine if covalent bonds are sigma bonds or pi bonds:
All single bonds are sigma bonds.
In multiple bonds, 1 pair of electrons is a sigma bond and all others are
pi bonds.

3. To Find the 3 Dimensional Shape of a Molecule:
VSEPR Theory = Valence Shell Electron Pair Repulsion Theory
This theory states that electron pairs around a central atom tend to be as
far apart as possible due to their repulsive force. In other words, the best arrangement of electrons is one that minimizes the repulsions among them.
Learn these 7 common shapes of molecules or 7 Molecular Geometries:
1.Tetrahedral
2. Trigonal pyramidal

4. 3. Bent - planar
4. Linear

5. Angle measure = 120 degrees
Examples: sulfur trioxide and boron trifluoride and
formaldehyde 5.
Angle measure = 90 and 120 degrees
Example: Phosphorus pentachloride 6.
Angle measure = 90 degrees
Example: Sulfur hexachloride 7.