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 covalent compounds have low melting and boiling points? And why covalent bond is directional in character?
Covalent compouns are linked together by covalent force of attraction due to which there exists less force of attraction between the binding molecules. As a result, less energy is required to break this bond. As a result, they have low melting and boiling point.
Covalent bonds are directional in nature because they are formed due to the overlapping of orbitals of two or more atoms that arrange each other in a way to maintain minimum repulsion and ensure maximum stability.