( ( ( The removal ) ( of ( ( orbital electrons ) ( from ( an atom ) ) ) ) ) ( ( is ( called ionization ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN removal)) (PP (IN of) (NP (NP (JJ orbital) (NNS electrons)) (PP (IN from) (NP (DT an) (NN atom)))))) (VP (VBZ is) (VP (VBN called) (NP (NN ionization)))) (. .)))
The removal of orbital electrons from an atom is called ionization.
(ROOT (S (NP (DT The) (NN orbital)) (VP (VBZ is) (NP (NP (DT the) (NN region)) (VP (VBN called) (SBAR (WHADVP (WRB where)) (S (NP (DT an) (NN electron)) (VP (VBZ is) (ADJP (RBS most) (JJ likely) (S (VP (TO to) (VP (VB be) (VP (VBN found)))))))))))) (. .)))