( ( If ( ( an atom ) ( ( ( loses or ) gains ) electrons ) ) ) ( , ( it ( ( is ( called ( an ion ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN If) (S (NP (DT an) (NN atom)) (VP (VBZ loses) (CC or) (VBZ gains) (NP (NNS electrons))))) (, ,) (NP (PRP it)) (VP (VBZ is) (VP (VBN called) (NP (DT an) (NN ion)))) (. .)))
If an atom loses or gains electrons , it is called an ion .
(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))) (. .)))