[vmelkon]

Isn't this something that is already known?

http://ca.news.yahoo.com/elemental-shift-periodic-table-gets-weight-changes-20101217-095003-312.html

The atomic mass varies depending on the isotopic mixture. Different sources of carbon give a different ratios of the C12 13 and 14 isotopes. The same goes for all other elements.

What is going on here. Good reporting or bad reporting?

[Borek]

Nothing new. Somewhere deep in the forum archives is discussion on the subject (sorry, I can't find it). If I recall correctly, boron has the largest variability of atomic mass depending on source.

[Hybrid]

but having mass range will be headache

[Borek]

No. In most cases you can safely ignore the problem. Wherever it is important, it is already a headache for those working in the area.