General chemistry: how to determine hybridization? how to know how many orbitals on an element

Question

General chemistry: how to determine hybridization? how to know how many orbitals on an element

Answer 1

it has to do with the bond angles and the amount of electrons in the S and P sub-oritals after bonding occurs, bond shape and amount of pi and sigma bonds

To determine it take the example of Carbon (since it is most commonly asked and can form single, double and triple bonds). In order to determine the hybridization on a carbon atom, one must first draw the Lewis structure. From the Lewis structure, count the number of groups around the central carbon. A group represents the regions of electron density around the carbon, and may be single, double or triple bonded. The number of groups represents how many hybrid orbitals have formed. The number of hybrid orbitals formed equals the number of atomic orbitals mixed. The description of the atomic orbitals mixed is equivalent to the hybridization of the carbon atom.

For our first example, CH4 (methane). The Lewis structure shows four groups around the carbon atom. This means four hybrid orbitals have formed. In order to form four hybrid orbitals, four atomic orbitals have been mixed. The s orbital and all three p orbitals have been mixed, thus the hybridization is sp3 .The four sp3 hybrid orbitals will arrange themselves in three dimensional space to get as far apart as possible (to minimize repulsion). The geometry that achieves this is tetrahedral geometry, where any bond angle is 109.5 degrees.

Next, C2H4 (ethene). The Lewis structure show three groups around each carbon atom. This means three hybrid orbitals have formed for each carbon. In order to form three hybrid orbitals, three atomic orbitals have been mixed. The s orbital and two of the p orbitals for each carbon have been mixed, thus the hybridization for each carbon is sp2. The three sp2 hybrid orbitals will arrange themselves in three dimensional space to get as far apart as possible. The geometry that achieves this is trigonal planar geometry, where the bond angle between the hybrid orbitals is 120 degrees. The unmixed pure p orbital will be perpendicular to this plane. Keep in mind, each carbon atom is sp2 , and trigonal planar.

Finally, C2H2 (acetylene). The Lewis structure shows two groups around each carbon atom. This means two hybrid orbitals have formed. In order to form two hybrid orbitals, two atomic orbitals have been mixed. The two sp hybrid orbitals arrange themselves in three dimensional space to get as far apart as possible. The geometry which achieves is linear geometry with a bond angle of 180 degreese The two pure p orbitals which were not mixed are perpendicular to each other. The triple bond consists of one sigma bond and two pi bonds. The geometry around each carbon is linear with a bond angle of 180d degreese

Answer 2

Look at how many electrons there are. Fill the orbitals (1s, 2s, 2p, and so on...) Combine the top two highest orbital shells together and fill them according to the building up principle. Looking at a lewis structure can help determine the number of unhybridized orbitals that remain.