( ( ( The number ) ( of ( electrons ( in ( an atom ) ) ) ) ) ( ( ( ( is ( equal ( to ( ( the number ) ( of protons ) ) ) ) ) , ) ( so ( that ( ( ( the ( hydrogen atom ) ) ( with ( one proton ) ) ) ( has ( one electron ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN number)) (PP (IN of) (NP (NP (NNS electrons)) (PP (IN in) (NP (DT an) (NN atom)))))) (VP (VBZ is) (ADJP (JJ equal) (PP (TO to) (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NNS protons)))))) (, ,) (SBAR (RB so) (IN that) (S (NP (NP (DT the) (NN hydrogen) (NN atom)) (PP (IN with) (NP (CD one) (NN proton)))) (VP (VBZ has) (NP (CD one) (NN electron)))))) (. .)))
The number of electrons in an atom is equal to the number of protons, so that the hydrogen atom with one proton has 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))))) (. .)))