( ( The ( simplest atom ) ) ( ( ( ( is ( ( the one ) ( of hydrogen ) ) ) , ) ( with ( just ( one electron ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJS simplest) (NN atom)) (VP (VBZ is) (NP (NP (DT the) (NN one)) (PP (IN of) (NP (NN hydrogen)))) (, ,) (PP (IN with) (NP (RB just) (CD one) (NN electron)))) (. .)))
The simplest atom is the one of hydrogen, with just one electron.
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD one) (NNS electrons)) (PP (IN in) (NP (DT the) (NN hydrogen) (NN atom))))) (. .)))