NH3, or ammonia, is a polar molecule. A polar molecule is one that has a positive charge on one side and a negative charge on the other. A polar molecule is formed when a highly electronegative atom bonds with an electronegative atom having less charge.
The trigonal pyramidal arrangement of the atoms in the ammonia molecule contributes to its polarity. The nitrogen atom in the ammonia molecule has an electron pair, which makes ammonia a proton acceptor. The polarity of the ammonia molecule makes it miscible with water. In high concentrations, ammonia is corrosive and hazardous. Household ammonia is a solution of ammonia in water.