( e.g. ( , ( ( a ( carbon atom ) ) ( ( ( ( has ( six protons ) ) but ) ( may ( have ( ( ( more or ) less ) ( than ( usual ( six neutrons ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (ADVP (RB e.g.)) (, ,) (NP (DT a) (NN carbon) (NN atom)) (VP (VP (VBZ has) (NP (CD six) (NNS protons))) (CC but) (VP (MD may) (VP (VB have) (NP (NP (JJR more) (CC or) (JJR less)) (PP (IN than) (NP (JJ usual) (CD six) (NNS neutrons))))))) (. .)))
e.g., a carbon atom has six protons but may have more or less than usual six neutrons.
(ROOT (S (NP (DT All) (NN carbon) (NNS atoms)) (VP (VBP have) (NP (CD six) (NNS protons))) (. .)))