NH3 - Ammonia:
First draw the Lewis dot structure:
![NH3 Lewis Structure](http://www.tutor-homework.com/Chemistry_Help/Molecular_Geometry/NH3.jpg)
Electron geometry: tetrahedral. Hybridization: sp3
Then draw the 3D molecular structure using VSEPR rules:
The molecular geometry of NH3 is trigonal pyramidal with asymmetric charge distribution on the central atom.
Therefore this molecule is polar.
Ammonia on Wikipedia.
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