( ( ( A ( free neutron ) ) ( -LRB- ( ( ( one not ) ( contained ( in ( an ( atomic nucleus ) ) ) ) ) -RRB- ) ) ) ( ( is radioactive ) . ) )
(ROOT (S (NP (NP (DT A) (JJ free) (NN neutron)) (PRN (-LRB- -LRB-) (VP (ADVP (NP (CD one)) (RB not)) (VBN contained) (PP (IN in) (NP (DT an) (JJ atomic) (NN nucleus)))) (-RRB- -RRB-))) (VP (VBZ is) (ADJP (JJ radioactive))) (. .)))
A free neutron (one not contained in an atomic nucleus) is radioactive .
(ROOT (S (NP (NP (DT The) (NN atom)) (PP (IN in) (NP (DT a) (NN neutron)))) (VP (VBZ is) (VP (VBN found) (PP (IN in) (NP (DT the) (DT the) (NN nucleus))))) (. .)))