Hydrogen Bonding

Para-hydrogen and ortho-hydrogen are two different spin isomers of molecular hydrogen (H ). These two forms differ in the orientation of the spins of the protons (nuclei of hydrogen atoms) in the H molecule. - Para-hydrogen: In this form, the spins of the two protons are opposite, meaning they have anti-parallel spins. - Ortho-hydrogen: In this form, the spins of the two protons are parallel. The difference in the arrangement of the proton spins is the key distinction between para- and ortho-hydrogen, which is why the correct answer is (D) Spins of protons.