( ( An ion ) ( ( is ( when ( ( ( ( ( an ( atom losses ) ) or ) gain ) an ) electron ) ) ) . ) )
(ROOT (S (NP (DT An) (NN ion)) (VP (VBZ is) (SBAR (WHADVP (WRB when)) (S (NP (NP (DT an) (NN atom) (NNS losses)) (CC or) (NP (NN gain)) (DT an)) (VP (VBP electron))))) (. .)))
An ion is when an atom losses or gain an electron.
(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))) (. .)))