( ( ( ( In order ) ( to ( prove ( that ( something ( ( is not ) ( an element ) ) ) ) ) ) ) ( , ( all ( you ( have ( to do ) ) ) ) ) ) ( ( ( ( ( is chemically ) decompose ) it ) ( into ( simpler ( pure substances ) ) ) ) . ) )
(ROOT (SINV (S (SBAR (IN In) (NN order) (S (VP (TO to) (VP (VB prove) (SBAR (IN that) (S (NP (NN something)) (VP (VBZ is) (RB not) (NP (DT an) (NN element))))))))) (, ,) (RB all) (NP (PRP you)) (VP (VBP have) (S (VP (TO to) (VP (VB do)))))) (VP (VBZ is) (ADVP (RB chemically)) (ADJP (JJ decompose))) (NP (PRP it)) (PP (IN into) (NP (JJR simpler) (JJ pure) (NNS substances))) (. .)))
In order to prove that something is not an element, all you have to do is chemically decompose it into simpler pure substances.
(ROOT (S (NP (NNS Elements)) (VP (VBP are) (NP (NP (JJ pure) (NNS substances)) (SBAR (WHNP (WDT that)) (S (VP (VBP make) (ADVP (RB up) (DT all) (NN matter))))))) (. .)))