what shape would you expect a molecule to hove that was based on an atom with only two bonding pairs of electrons? Three bonding pairs? Four?
Here is a good site. Scroll down to the heading AXE method.
http://en.wikipedia.org/wiki/VSEPR_theory
Thanks got it now!
To determine the shape of a molecule, we need to follow a few steps:
1. Draw the Lewis structure: Start by drawing the Lewis structure of the molecule, which represents the arrangement of atoms and valence electrons. Valence electrons are the electrons involved in bonding.
2. Determine the number of bonding pairs: Count the number of bonding pairs of electrons around the central atom. A bonding pair is a pair of electrons involved in a chemical bond.
Now, let's consider the shapes based on the number of bonding pairs:
1. Two bonding pairs: If the central atom has only two bonding pairs, the molecule will have a linear shape. The bond angle between the two bonded atoms is 180 degrees. An example of a molecule with two bonding pairs is carbon dioxide (CO2).
O=C=O
2. Three bonding pairs: If the central atom has three bonding pairs, the molecule will have a trigonal planar shape. The bond angles between the three bonded atoms are 120 degrees. An example of a molecule with three bonding pairs is boron trichloride (BCl3).
Cl
|
B-Cl
|
Cl
3. Four bonding pairs: If the central atom has four bonding pairs, the molecule will have a tetrahedral shape. The bond angles between the four bonded atoms are 109.5 degrees. An example of a molecule with four bonding pairs is methane (CH4).
H
|
H-C-H
|
H
By following these steps, we can determine the shape of a molecule based on the number of bonding pairs of electrons around the central atom.