( ( An atom ) ( ( can ( ( ( ( ( gain or ) lose ) electrons ) , ) ( becoming ( what ( is ( known ( as ( an ion ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT An) (NN atom)) (VP (MD can) (VP (VB gain) (CC or) (VB lose) (NP (NNS electrons)) (, ,) (S (VP (VBG becoming) (SBAR (WHNP (WP what)) (S (VP (VBZ is) (VP (VBN known) (PP (IN as) (NP (DT an) (NN ion))))))))))) (. .)))
An atom can gain or lose electrons, becoming what is known as 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))) (. .)))