( ( ( ( ( ( ( Atoms , ) molecules ) , ) ions ) , ) ( chemical bonding ) ) . )
(ROOT (NP (NP (NNS Atoms)) (, ,) (NP (NNS molecules)) (, ,) (NP (NNS ions)) (, ,) (NP (NN chemical) (NN bonding)) (. .)))
Atoms, molecules, ions, chemical bonding.
(ROOT (S (NP (DT A) (-LRB- -LRB-) (NN n) (-RRB- -RRB-) (NN chemical) (NN bond)) (VP (VBZ is) (NP (NP (DT a) (NN force)) (PP (IN of) (NP (NP (NN attraction)) (PP (IN between) (NP (NNS ions) (CC and) (NNS atoms))))))) (. .)))