Bum8ara5h: Maybe also kindly let us know how u decrypted it
Palestine: If the solver does not, I will. (^_^)
Thanks Palestine for the write-up. I missed this nice puzzle, but I don't think I'd gotten it anyway. Especially since, for example, if I look up roentgenium I find its atomic mass to be 282, as it's by far its most stable known isotope it seems. I wondered why NIST rather picked 280 and also saw that that Royal Society of Chemistry
lists 280 as its "key isotope", but I guess it's just because both 281 and 282 were the last ones to be discovered (in 2010) and those data are simply not up-to-date (in case anyone cared!). Anyway,that would likely have thrown me off.
Well done to those who cracked it though!