( ( ( ( Carbon-12 , ) ( ( the ( ( most ( ( common and ) stable ) ) isotope ) ) ( of carbon ) ) ) , ) ( ( has ( ( ( 6 protons ) and ) ( ( 6 neutrons ) ( ( an d ) ( therefore ( has ( ( an ( atomic mass ) ) ( of 12 ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Carbon-12)) (, ,) (NP (NP (DT the) (ADJP (RBS most) (JJ common) (CC and) (JJ stable)) (NN isotope)) (PP (IN of) (NP (NN carbon)))) (, ,)) (VP (VBZ has) (NP (NP (CD 6) (NNS protons)) (CC and) (NP (NP (CD 6) (NNS neutrons)) (SBAR (S (NP (DT an) (NN d)) (ADVP (RB therefore)) (VP (VBZ has) (NP (NP (DT an) (JJ atomic) (NN mass)) (PP (IN of) (NP (CD 12)))))))))) (. .)))
Carbon-12, the most common and stable isotope of carbon, has 6 protons and 6 neutrons an d therefore has an atomic mass of 12.
(ROOT (S (NP (NP (DT A) (NN carbon) (NN atom)) (PP (IN with) (NP (NP (CD 6) (NNS protons)) (CC and) (NP (CD 8) (NNS neutrons))))) (VP (VBZ is) (ADVP (RBR more) (RB specifically)) (VP (VBN known) (PP (IN as) (NP (NN carbon) (CD 14))))) (. .)))
A carbon atom with 6 protons and 8 neutrons is more specifically known as carbon 14.