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.

3 comments :

  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.)

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

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

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