( Anions ( ( are ( ( ( atoms or ) radicals ) ( which ( are ( ( a group ) ( of ( ( atoms , ) ( that ( have ( gained electrons ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Anions)) (VP (VBP are) (NP (NP (NNS atoms) (CC or) (NNS radicals)) (SBAR (WHNP (WDT which)) (S (VP (VBP are) (NP (NP (DT a) (NN group)) (PP (IN of) (NP (NP (NNS atoms)) (, ,) (SBAR (WHNP (WDT that)) (S (VP (VBP have) (VP (VBN gained) (NP (NNS electrons)))))))))))))) (. .)))
Anions are atoms or radicals which are a group of atoms, that have gained electrons.
(ROOT (S (NP (NNS Anions)) (VP (VBP are) (VP (VBN formed) (PP (IN by) (NP (NP (NNS atoms)) (VP (VBG gaining) (NP (NNS electrons))))))) (. .)))