( atoms ( ( may ( share ( ( one pair ) ( of ( ( ( ( ( ( electrons ( -LRB- ( ( single bonds ) -RRB- ) ) ) , ) ( ( two pairs ) ( -LRB- ( ( double bonds ) -RRB- ) ) ) ) , ) or ) ( ( three pairs ) ( -LRB- ( ( triple bonds ) -RRB- ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS atoms)) (VP (MD may) (VP (VB share) (NP (NP (CD one) (NN pair)) (PP (IN of) (NP (NP (NP (NNS electrons)) (PRN (-LRB- -LRB-) (NP (JJ single) (NNS bonds)) (-RRB- -RRB-))) (, ,) (NP (NP (CD two) (NNS pairs)) (PRN (-LRB- -LRB-) (NP (JJ double) (NNS bonds)) (-RRB- -RRB-))) (, ,) (CC or) (NP (NP (CD three) (NNS pairs)) (PRN (-LRB- -LRB-) (NP (JJ triple) (NNS bonds)) (-RRB- -RRB-)))))))) (. .)))
atoms may share one pair of electrons (single bonds), two pairs (double bonds), or three pairs (triple bonds).
(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))) (. .)))