( Anions ( ( are ( formed ( when ( ( ( an ( ( atom or ) group ) ) ( of atoms ) ) ( gains ( ( ( one or ) more ) electrons ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Anions)) (VP (VBP are) (VP (VBN formed) (SBAR (WHADVP (WRB when)) (S (NP (NP (DT an) (NN atom) (CC or) (NN group)) (PP (IN of) (NP (NNS atoms)))) (VP (VBZ gains) (NP (QP (CD one) (CC or) (JJR more)) (NNS electrons))))))) (. .)))
Anions are formed when an atom or group of atoms gains one or more electrons.
(ROOT (S (NP (DT A) (PRN (-LRB- -LRB-) (NP (NN n)) (-RRB- -RRB-)) (NN anion)) (VP (VBZ is) (VP (VBN formed) (SBAR (WHADVP (WRB when)) (S (NP (DT an) (NN element)) (VP (VBZ gains) (NP (QP (CD one) (CC or) (JJR more)) (NNS electrons))))))) (. .)))