( Radioactivity ( ( ( ( is ( ( the property ) ( of ( certain atoms ) ) ) ) ( -LRB- ( ( which ( ( are not ) stable ) ) -RRB- ) ) ) ( to ( spontaneously ( disintegrate ( by ( ( emitting ( ( either ( energetic ( ( particles or ) rays ) ) ) ( of ( ( pure energy ) ( -LRB- ( ( or both ) -RRB- ) ) ) ) ) ) ( from ( ( the ( ( nucleus or ) centre ) ) ( of ( the atom ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Radioactivity)) (VP (VP (VBZ is) (NP (NP (DT the) (NN property)) (PP (IN of) (NP (JJ certain) (NNS atoms))))) (PRN (-LRB- -LRB-) (SBAR (WHNP (WDT which)) (S (VP (VBP are) (RB not) (ADJP (JJ stable))))) (-RRB- -RRB-)) (S (VP (TO to) (VP (ADVP (RB spontaneously)) (VB disintegrate) (PP (IN by) (S (VP (VBG emitting) (NP (NP (DT either) (JJ energetic) (NNS particles) (CC or) (NNS rays)) (PP (IN of) (NP (NP (JJ pure) (NN energy)) (PRN (-LRB- -LRB-) (FRAG (CC or) (NP (DT both))) (-RRB- -RRB-))))) (PP (IN from) (NP (NP (DT the) (NN nucleus) (CC or) (NN centre)) (PP (IN of) (NP (DT the) (NN atom)))))))))))) (. .)))
Radioactivity is the property of certain atoms (which are not stable) to spontaneously disintegrate by emitting either energetic particles or rays of pure energy (or both) from the nucleus or centre of the atom.
(ROOT (S (NP (NNP Radioactivity)) (VP (VP (VBZ is) (NP (NP (DT the) (NN release)) (PP (IN of) (NP (NNS particles))))) (CC and/or) (VP (NP (NN energy)) (PP (IN from) (NP (NP (DT the) (NN nucleus)) (PP (IN of) (NP (DT an) (NN atom))))))) (. .)))