( ( ( The rate ) ( of ( decay ( of ( a ( radioactive isotope ) ) ) ) ) ) ( ( is ( called ( ( ( its ( half life ) ) , ) ( ( the time ) ( ( in which ) ( ( ( half ( the ( initial amount ) ) ) ( of atoms ) ) ( present ( takes ( to ( decay ( -LRB- ( ( Figure 1 ) -RRB- ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN rate)) (PP (IN of) (NP (NP (NN decay)) (PP (IN of) (NP (DT a) (JJ radioactive) (NN isotope)))))) (VP (VBZ is) (VP (VBN called) (NP (NP (PRP$ its) (JJ half) (NN life)) (, ,) (NP (NP (DT the) (NN time)) (SBAR (WHPP (IN in) (WHNP (WDT which))) (S (NP (NP (PDT half) (DT the) (JJ initial) (NN amount)) (PP (IN of) (NP (NNS atoms)))) (ADVP (RB present)) (VP (VBZ takes) (PP (TO to) (NP (NP (NN decay)) (PRN (-LRB- -LRB-) (NP (NN Figure) (CD 1)) (-RRB- -RRB-))))))))))) (. .)))
The rate of decay of a radioactive isotope is called its half life, the time in which half the initial amount of atoms present takes to decay (Figure 1).
(ROOT (S (NP (DT The) (NN term) (NN half-life)) (VP (VBZ decribes) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (NN time)) (VP (VBN required) (PP (IN for) (NP (NP (NN half)) (PP (IN of) (NP (DT the) (JJ original) (NN material))))) (PP (TO to) (NP (NP (NN decay)) (PP (IN in) (NP (DT an) (NN isotope)))))))))) (. .)))