( ( Triple bonds ) ( occasionally ( ( form ( when ( ( ( three pairs ) ( of electrons ) ) ( are ( shared ( between ( two atoms ) ) ) ) ) ) ) . ) ) )
(ROOT (S (NP (JJ Triple) (NNS bonds)) (ADVP (RB occasionally)) (VP (VBP form) (SBAR (WHADVP (WRB when)) (S (NP (NP (CD three) (NNS pairs)) (PP (IN of) (NP (NNS electrons)))) (VP (VBP are) (VP (VBN shared) (PP (IN between) (NP (CD two) (NNS atoms)))))))) (. .)))
Triple bonds occasionally form when three pairs of electrons are shared between two atoms.
(ROOT (S (PP (IN In) (NP (DT a) (NN carbon) (JJ triple) (NN bond))) (, ,) (NP (NP (CD three) (NNS pairs)) (PP (IN of) (NP (NNS electrons)))) (VP (VBP are) (VP (VBN shared))) (. .)))