( Oxidation ( ( occurs ( when ( ( an ( ( atom or ) ion ) ) ( loses ( ( ( one or ) more ) electrons ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Oxidation)) (VP (VBZ occurs) (SBAR (WHADVP (WRB when)) (S (NP (DT an) (NN atom) (CC or) (NN ion)) (VP (VBZ loses) (NP (QP (CD one) (CC or) (JJR more)) (NNS electrons)))))) (. .)))
Oxidation occurs when an atom or ion loses one or more electrons.
(ROOT (S (NP (DT Some) (NNS atoms)) (VP (VBP are) (ADJP (ADJP (RBR more) (JJ stable)) (SBAR (WHADVP (WRB when)) (S (NP (PRP they)) (VP (VB gain) (CC or) (VB lose) (NP (DT an) (NN electron) (CC and) (NN form) (NNS ions))))))) (. .)))