( There ( ( are ( ( ( ( approximately 270 ) ( stable isotopes ) ) and ) ( 50 ( naturally ( occurring ( radioisotopes ( -LRB- ( ( radioactive isotopes ) -RRB- ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (QP (RB approximately) (CD 270)) (JJ stable) (NNS isotopes)) (CC and) (NP (NP (CD 50)) (VP (ADVP (RB naturally)) (VBG occurring) (NP (NP (NNS radioisotopes)) (PRN (-LRB- -LRB-) (NP (JJ radioactive) (NNS isotopes)) (-RRB- -RRB-))))))) (. .)))
There are approximately 270 stable isotopes and 50 naturally occurring radioisotopes (radioactive isotopes).
(ROOT (S (NP (DT A) (-LRB- -LRB-) (NN n) (-RRB- -RRB-) (NNS radioisotopes)) (VP (VBZ is) (NP (NP (DT an) (NN isotope)) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (ADJP (JJ radioactive))))))) (. .)))