( ( ( energy-level shell ) ( ( The distribution ) ( of ( electrons ( around ( ( the nucleus ) ( of ( an atom ) ) ) ) ) ) ) ) . )
(ROOT (NP (NP (JJ energy-level) (NN shell)) (NP (NP (DT The) (NN distribution)) (PP (IN of) (NP (NP (NNS electrons)) (PP (IN around) (NP (NP (DT the) (NN nucleus)) (PP (IN of) (NP (DT an) (NN atom)))))))) (. .)))
energy-level shell The distribution of electrons around the nucleus of an atom.
(ROOT (S (NP (DT An) (NN electron)) (VP (VBZ moves) (PP (TO to) (NP (NP (DT a) (NN shell)) (ADVP (RB farther) (PP (IN from) (NP (DT the) (NN nucleus)))))) (SBAR (IN after) (S (NP (PRP it)) (VP (VBZ absorbs) (NP (NN energy)))))) (. .)))