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.
Draw the orbit structure of Ethyne
Now, one 2s and one 2p orbitals undergo sp hybridization to form two sp hybrid orbitals of equivalent energy and identical shape and size which take linear geometry with bond angle 180º. Unhybridized 2py and 2pz orbitals remain perpendicular to hybrid orbitals. One half filled sp hybrid orbital of carbon atom overlaps with half-filled sp orbital of another carbon atom forming carbon to carbon sigma bond. The remaining half filled sp orbitals of each carbon overlaps with half-filled 1s orbital of two hydrogen atoms forming two carbons to hydrogen sigma bonds. Unhybridized and half-filled 2py and 2pz orbitals of one carbon overlap with respective orbitals of another carbon laterally forming two carbon to carbon pi bonds.