Sentence:  The nuclear dipole effects provide some information on the motions of the <WSD>hydrogen</WSD> nuclei , but the symmetry of the **f bond in **f remains in doubt . 
Meaning of the word marked with <WSD> tags:  a nonmetallic univalent element that is normally a colorless and odorless highly flammable diatomic gas; the simplest and lightest and most abundant element in the universe