Nitrogen forming three pyramidal bonds

The four sp3 orbitals for these three atoms (i.e. N, O and Cl) form a tetrahedral arrangement having one or more of the hybridised orbitals occupied by a lone pair of electrons. For an isolated atom, nitrogen forms a pyramidal shape where the bond angles are slightly less than 109.5 (c. 107 )fig.(a). This compression of the bond angles is because of the orbital containing the lone... 

Such strong inward pyramidalization of the nitrogens is stabilized by the overlapping of the nitrogen electrons forming a two-center three-electron bond in the cation radi-... 

Finally with nitrogen the bonding of three hydrogen atoms to form NH3, ammonia, takes place through three unpaired p electrons along three mutually perpendicular axes. The molecular structure of ammonia is indeed that of a three-sided pyramid for the same reason as in the water molecule the valency angle is also increased in this case to 105°. 

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