( Hydrogen ( ( is ( ( ( the ( simplest atom ) ) , ) ( with ( only ( one electron ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Hydrogen)) (VP (VBZ is) (NP (NP (DT the) (JJS simplest) (NN atom)) (, ,) (PP (IN with) (NP (RB only) (CD one) (NN electron))))) (. .)))
Hydrogen is the simplest atom, with only 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))))) (. .)))