( ( ( Thus ( a ( stable element ) ) ) ( such ( as Carbon ) ) ) ( has ( ( ( a nucleus ) ( with ( ( ( six protons ) and ) ( six neutrons ) ) ) ) ( which ( may ( be ( ( written ( as ( 12 6 ) ) ) ( ( ( C or ) simply ) ( 12 C. ) ) ) ) ) ) ) ) )
(ROOT (S (NP (NP (ADVP (RB Thus)) (DT a) (JJ stable) (NN element)) (PP (JJ such) (IN as) (NP (NNP Carbon)))) (VP (VBZ has) (NP (NP (DT a) (NN nucleus)) (PP (IN with) (NP (NP (CD six) (NNS protons)) (CC and) (NP (CD six) (NNS neutrons)))) (SBAR (WHNP (WDT which)) (S (VP (MD may) (VP (VB be) (VP (VBN written) (PP (IN as) (NP (QP (CD 12) (CD 6)))) (NP (NP (NNP C)) (CC or) (ADVP (RB simply)) (NP (CD 12) (NNP C.))))))))))))
Thus a stable element such as Carbon has a nucleus with six protons and six neutrons which may be written as 12 6 C or simply 12 C.
(ROOT (S (NP (NNP Carbon) (NNS atoms)) (VP (VBP have) (NP (NP (CD six) (NNS neutrons)) (CONJP (RB as) (RB well) (IN as)) (NP (CD six) (NNS protons)))) (. .)))