metaclass

Even though I’m no spring chicken, I still have regular “AHA!” moments where something that puzzled me or got little notice from me suddenly falls into place. And I’m glad I do still have these moments, because they’re so much fun. I wonder how I missed things that in hindsight seem so obvious. And I’m never sure whether I’m in the minority or majority with each of these gaps in knowledge as they come up.

Anyway, I just had one of those moments. I was reading a post in a blog on statistical modeling, and I followed the link to the paper cited. And in reading the abstract, I suddenly realized why it’s called the periodic table.

Of course I know what periodic means, and I learned a bit about the periodic table in my two chemistry classes. But I guess I never asked myself why it’s called the periodic table. Now I realize it’s because, for at least a certain portion of the table, elements 18 “units” apart from another share certain properties. So there’s a periodicity of 18 for part of the table. Whoa!

I suppose part of the reason is that when I learned about properties of the elements in the periodic table, I was probably about twelve, and the word periodic didn’t mean much to me. But I took one other course in chemistry as an undergrad, and I must have understood what periodic meant by then….

Does everyone know this and I just somehow missed it?