( ( ( ( kinetic ( and ( potential energies ) ) ) ( of ( the ( ( electrons and ) nuclei ) ) ) ) ( in molecules ) ) . )
(ROOT (NP (NP (JJ kinetic) (CC and) (JJ potential) (NNS energies)) (PP (IN of) (NP (DT the) (NNS electrons) (CC and) (NNS nuclei))) (PP (IN in) (NP (NNS molecules))) (. .)))
kinetic and potential energies of the electrons and nuclei in molecules.
(ROOT (S (NP (NP (DT The) (NN sum)) (PP (IN of) (NP (NP (DT the) (JJ kinetic) (CC and) (JJ potential) (NNS energies)) (PP (IN of) (NP (NP (DT a) (NN system) (POS 's)) (NNS atoms) (CC and) (NNS molecules)))))) (VP (VBZ is) (VP (VBN called) (NP (JJ internal) (NN energy)))) (. .)))