( ( For instance ) ( , ( ( hydrogen atoms ) ( ( have ( ( one ( outer electron ) ) ( -LRB- ( ( 1 ( s 1 ) ) -RRB- ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN For) (NP (NN instance))) (, ,) (NP (NN hydrogen) (NNS atoms)) (VP (VBP have) (NP (NP (CD one) (JJ outer) (NN electron)) (PRN (-LRB- -LRB-) (NP (QP (CD 1) (IN s) (CD 1))) (-RRB- -RRB-)))) (. .)))
For instance, hydrogen atoms have one outer electron (1 s 1 ).
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD one) (NNS electrons)) (PP (IN in) (NP (DT the) (NN hydrogen) (NN atom))))) (. .)))