( ( An ion ) ( ( is ( ( an atom ) ( that ( ( ( has lost ) or ) ( gained electrons ) ) ) ) ) . ) )
(ROOT (S (NP (DT An) (NN ion)) (VP (VBZ is) (NP (NP (DT an) (NN atom)) (SBAR (WHNP (WDT that)) (S (VP (VP (VBZ has) (VP (VBN lost))) (CC or) (VP (VBD gained) (NP (NNS electrons)))))))) (. .)))
An ion is an atom that has lost or gained electrons.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (DT an) (NN atom)) (VP (VBZ gains) (CC or) (VBZ loses) (NP (DT an) (NN electron))))) (NP (PRP it)) (VP (VBZ becames) (NP (DT a) (PRN (-LRB- -LRB-) (NP (NN n)) (-RRB- -RRB-)) (NN ion))) (. .)))