Henry: I read your blog post--you forgot about Döbereiner.
Henry: Döbereiner. Johann Döbereiner. He was before Newlands. He arranged elements into triads.
Me: What are triads?
Henry: Döbereiner's Triads. Groups of three elements. All related.
Me: That's pretty scanty.
Henry: So, are we going to play cards or what?
Me: OK. What are we playing?
Henry had a special deck of cards, each one a different chemical element instead of the usual playing card. I took out everything but the D-block elements (Sc through Hg) shuffled them, and then dealt us each five cards, face down.