( ( ( ( Hydrogen Atom ) ( -LRB- ( ( ( ( energy levels ) , ) ( ( wave-particle duality ) ( for electron ) ) ) -RRB- ) ) ) 6 ) . )
(ROOT (NP (NP (NP (NNP Hydrogen) (NNP Atom)) (PRN (-LRB- -LRB-) (NP (NP (NN energy) (NNS levels)) (, ,) (NP (NP (JJ wave-particle) (NN duality)) (PP (IN for) (NP (NN electron))))) (-RRB- -RRB-))) (ADJP (CD 6)) (. .)))
Hydrogen Atom ( energy levels, wave-particle duality for electron ) 6.
(ROOT (S (NP (DT The) (NN spectrum)) (VP (VBZ is) (VP (VBN made) (PRT (RP up)) (PP (IN of) (NP (NP (JJ discrete) (NNS lines)) (VP (VBG representing) (NP (NP (NNS transitions)) (PP (IN of) (NP (NP (DT the) (NN hydrogen) (NN electron)) (PP (IN between) (NP (JJ specific) (NN energy) (NNS levels)))))) (PP (IN within) (NP (DT the) (NN atom)))))))) (. .)))