Friday 14 June 2013

Helical Periodic Table - Part II

Well, it didn't take long for someone to point out mistakes in the periodic tables I put together ... and in a pub, of all places! The stable mass numbers of some of the heavier elements were all wrong. I've now corrected the PDFs. But looking through the numbers again I noticed an interesting anomaly.

In a few places, the standard atomic weights [say W] (observed in nature) do not increase monotonically with the atomic number [say Z]. For instance:
  • Argon, Z=18, W=39.948
  • Potassium, Z=19, W=39.048
Wikipedia tells me this is all to do with the relative prevalence of naturally occurring isotopes. But I'm not 100% sure I fully understand all the subtleties. I suspect my lack of understanding will not inhibit my everyday life, however.


  1. I just found your helical periodic table and think it is brilliant! I was trying to come up with something similar of my own and you have saved me much work. I would like to use the pdf with my uni students this coming semester if that's ok with you.

    One nitpick--the group that contains helium, neon, and so forth should be called the "noble gases"--not the "nobel gases." (The latter category, I imagine, should be reserved for gases that have won the Nobel prize. Alas, Einsteinium and Curium aren't gases.)

  2. Hi unlikelygrad. Of course you can use the PDF and I'll get right onto fixing the typo!

  3. @unlikelygrad: I've corrected the spelling and uploaded the new versions in SVG format for more flexibility. See the original post for links.