To find out that NH3 is polar or non polar, first of all we should differentiate between polar and non polar.
A polar molecule is that which has two poles partial positive and partial negative and whose dipole did not cancel each other’s effect and get net dipole as a product of the opposite charges formed polar bonds asymmetrically. Just like a magnet having two poles, the polar molecules also hold two poles that grab two opposed charges.
A non-polar molecule is that which have equal sharing of electrons between the two atoms of a diatomic molecule or symmetrical arrangement of polar bonds in a complex molecule. No partial charge will exist in such molecules.
Characteristics of ammonia:
Chemical formula of ammonia is NH3. It is a colorless gas used for manufacturing of fertilizer, also used for production of nitrogenous compounds.
The question arise that, is ammonia a polar or nonpolar molecule?
We can say that ammonia is a polar molecule, with its polarity being prejudiced by its asymmetrical shape and due to the presence of the nitrogen and hydrogen atoms surrounded by it. In ammonia molecule nitrogen is highly electronegative than hydrogen which makes electronegativity difference and induces polarity.
Following are some characteristics which show that ammonia is polar molecule.
The electronegativity difference among hydrogen and nitrogen is almost nine so that it forms partially polar bonds. Therefore we can say NH3 is a polar bond.
Structure of NH3:
Nitrogen has seven atomic number having five valence electrons. Three electrons make bonds with hydrogen and two lone pairs are present on nitrogen. These lone pairs repel the surrounding hydrogen. In this way the lone pair of electrons on the nitrogen atom get partial negative charge δ− on other hand 3 hydrogen atoms found partial positive charge δ+ .The shape of the molecule slightly bent downward and the bond angle formed almost 107° instead of 109.5, which produce a permanent dipole among ammonia molecule. This makes it a polar molecule. If the structure of NH3 will be planner then the middle of negative and positive charges would overlap and the molecule would be nonpolar but in real NH3 molecule looks more like a tetrahedron.
Shape of NH3:
The shape of NH3 is trigonal pyramidal which is asymmetrical. And asymmetrical molecules show polar behavior because it’s both sides are not identical.
If a molecule has zero dipole moment then it will be non polar. NH3 has a none zero dipole moment so it is a polar molecule.