Again we need a hybrid orbital for each atom and pair of non-bonding electrons. Ammonia has three hydrogen atoms and one non-bonded pair of electrons when we draw the electron-dot formula. In order to determine the hybridization of an atom, you must first draw the electron-dot formula.
Even with a lone electron pair and 2 sigma bonds, there are 3 electron regions, it is still referred to as sp2 hybridization. An example of a molecule with 2 sigma bonds and a lone pair of electrons is S0 2. Tetrahedral Molecular Geometry. With 4 sigma bonds and no lone pairs there are 4 electron regions and the molecular shape is tetrahedral.
Hybridization of Atomic Orbitals and the Shape of Molecules. If the four hydrogen atoms in a methane molecule (CH 4) were bound to the three 2p orbitals and the 2s orbital of the carbon atom, the H-C-H bond angles would be 90 o for 3 of the hydrogen atoms and the 4th hydrogen atom would be at 135 o from the others.
Finally divide the whole by 2 & you will get the hybridization. Now for CH4 - C is the central atom & has 4 valence electrons. Four hydrogen atoms are bonded by four single bonds. So according to the trick 4+4 =8. Dividing 8 by 2 we get 4 i.e. sp3 (tetrahedral).