settle a debate about same mass compounds
 

:shock:
Me and my group are having an argument about the correct name for two different molecular species that have different composition, but the same mass. Some say that they are isobars, but I point out that that is generally only applicable for atmos, not molecules. However, I must admit I may be wrong, but I do seem to remember there being a specific word for it. I've searched my chemistry dictionary but so far got nothing. Can anybody help?

l-s

I don't know of any such term. Isobar literally translates to "same weight" so it would seem to be appropriate even for non atoms. This is the first time I've ever heard anyone mention such a term or the need for one.

I guess this is a non conclusive answer :? Sorry!

isomer

An isomer is a more restrictive term. Isomers have all the same numbers of the same kinds of atoms. Same mass molecules might have different composition with the same mass to the neared dalton.

They can't have the same mass and be of a different composition. At least not using anf FT-MS