( Carbon-12 ( ( is ( ( an isotope ) ( of carbon ) ) ) . ) )
(ROOT (S (NP (NNP Carbon-12)) (VP (VBZ is) (NP (NP (DT an) (NN isotope)) (PP (IN of) (NP (NN carbon))))) (. .)))
Carbon-12 is an isotope of carbon.
(ROOT (S (NP (NP (NNP Carbon) (CD 14) (NN isotope)) (PP (IN of) (NP (NN carbon)))) (VP (VBZ is) (ADVP (RB typically)) (VP (VBN used) (PP (TO to) (NP (NN date) (JJ ancient) (NNS items))))) (. .)))