( ( ( ( ( Carbon atoms ) , ) ( because ( of ( ( ( their ( small size ) ) and ) ( four ( available ( bonding electrons ) ) ) ) ) ) ) , ) ( ( can ( ( join ( to ( ( other ( carbon atoms ) ) ( in ( ( chains and ) rings ) ) ) ) ) ( to ( form ( ( ( large and ) complex ) molecules ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Carbon) (NNS atoms)) (, ,) (PP (RB because) (IN of) (NP (NP (PRP$ their) (JJ small) (NN size)) (CC and) (NP (CD four) (JJ available) (NN bonding) (NNS electrons)))) (, ,)) (VP (MD can) (VP (VB join) (PP (TO to) (NP (NP (JJ other) (NN carbon) (NNS atoms)) (PP (IN in) (NP (NNS chains) (CC and) (NNS rings))))) (S (VP (TO to) (VP (VB form) (NP (ADJP (JJ large) (CC and) (JJ complex)) (NNS molecules))))))) (. .)))
Carbon atoms, because of their small size and four available bonding electrons, can join to other carbon atoms in chains and rings to form large and complex molecules.
(ROOT (S (NP (CD Four) (JJ valence) (NNS electrons)) (VP (MD can) (VP (VB be) (VP (VBN found) (PP (IN in) (NP (DT a) (NN carbon) (NN atom)))))) (. .)))