Tetrahedral (AX4)
The Tetrahedral shape is a type of shape which a molecule takes form of when there are four faces or sides to the molecule, forming a regular tetrahedron shape. The bond angles are 109.5 degrees. The central atom should have no lone pairs attached to it and should only consist of 4 bonds. It is a non-polar shape since it is symmetrical. Here are some examples of tetrahedral shapes:
Methane
Carbon Tetrachloride
What contributes to this shape?
The only thing that contributes to this shape are the four bonds which the central atom is attached to. There are no lone pairs of electrons which would repel with the surrounding atoms and provide a different bond angle and shape. Since there are only 4 bonds attached to it and no lone pairs, the bond angles tend to be 109.5 degrees due to their inability to bend.