( ( Molecules ( which ( ( ( have ( the ( same formula ) ) ) , ) ( but ( ( ( different ( spatial arrangement ) ) ( of atoms ) ) ( , ( ( like ( this example ) ) ( , ( are called ) ) ) ) ) ) ) ) ) ( isomers . ) )
(ROOT (S (NP (NP (NNS Molecules)) (SBAR (WHNP (WDT which)) (S (VP (VBP have) (NP (DT the) (JJ same) (NN formula)) (, ,) (SBAR (CC but) (S (NP (NP (JJ different) (JJ spatial) (NN arrangement)) (PP (IN of) (NP (NNS atoms)))) (, ,) (PP (IN like) (NP (DT this) (NN example))) (, ,) (VP (VBP are) (VP (VBN called))))))))) (VP (VBZ isomers)) (. .)))
Molecules which have the same formula, but different spatial arrangement of atoms, like this example, are called isomers .
(ROOT (S (NP (NP (NNS Alkenes)) (PP (IN with) (NP (NP (DT the) (JJ same) (NNS atoms)) (PP (CC but) (NP (JJ different) (NNS shapes)))))) (VP (VBP are) (VP (VBN called) (NP (NNS isomers)))) (. .)))