Para and ortho hydrogen differ in:

Step-by-step solution

Hydrogen gas exists in two isomeric forms known as ortho-hydrogen and para-hydrogen. In ortho-hydrogen, the spins of the two nuclei (protons) are in the same direction (parallel). In para-hydrogen, the spins of the two nuclei (protons) are in opposite directions (antiparallel). Both forms have the same atomic number, the same number of neutrons (zero in the case of protium), and the same size, as they are both molecules of H₂ . Therefore, they differ only in the relative orientation of the nuclear spins. Answer: Sp