Which orbital is non directional?
They are non directional because they are spherical in shape and probability of finding electrons at a particular distance from the nucleus is same in all directions.
Why does NaCl dissolve in water ? And why are the ionic bonds non directional?
At the molecular level, salt dissolves in water due to the fact that both water and salt compounds are polar, with positive and negative charges on opposite sides in the molecule.
The positively-charged side of the water molecules are attracted to the negatively-charged chloride ions and the negatively-charged side of the water molecules are attracted to the positively-charged sodium ions.
Also, ionic bonds are non directional in nature since they are arranged in a lattice structure where every Positive ion is surrounded by negative ion on all sides, and same for the negative ions.