SP Hybridisation :
From Organic chemistry point of view Hybridisation can be calculated very simply by calculating
steric numbers.
Steric number is the sum of total sigma bonds and lone pair electrons on an atom.
For example in Allene ( CH2=C=CH2) , the central carbon has only 2 sigma bonds , two pi bonds and no lone pairs. Note that Pi bond is not counted in steric number. Here the steric number of Central Carbon atom is just 2, therefore Central Carbon atom is SP hybridised.
SP hybridised Carbon atom has Linear geometry and the ideal bond angle is 180
0.
In Allene , the Central carbon atom forms two sigma bonds, the valence-shell 2s orbital combines with one valence-shell 2p orbital to form
two equivalent sp mixed orbitals in a linear arrangement around the Central Carbon to form two sigma bonds with two different terminal Carbon atoms . One of the pure P orbital of Carbon overlap with another pure p orbital of terminal Carbon to form Pi bond.
Linear Geometry of Allene
See the animation of Allene
Other Examples : 2 Butyne
| Acetonitrile