' The atom was named before it was split.
( ' ( ( The atom ) ( ( was ( named ( before ( it ( was split ) ) ) ) ) . ) ) )
(ROOT (S ('' ') (NP (DT The) (NN atom)) (VP (VBD was) (VP (VBN named) (SBAR (IN before) (S (NP (PRP it)) (VP (VBD was) (VP (VBN split))))))) (. .)))
The atom was only named once it had been split.
( ( The atom ) ( ( ( was only ) ( named ( once ( it ( had ( been split ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN atom)) (VP (VBD was) (ADVP (RB only)) (VP (VBN named) (SBAR (IN once) (S (NP (PRP it)) (VP (VBD had) (VP (VBN been) (VP (VBN split)))))))) (. .)))