Metameric

a.
  1. (Chem.) Having the same molecular formula, but possessing a different bonding structure and different properties; as, methyl ether and ethyl alcohol are metameric compounds. See Isomeric.
  2. (Biol.) Of or pertaining to a metamere or its formation; as, metameric segmentation.

The existence of metameric compounds is due to different arrangements of the same atoms in the molecule.