from yesteryears' classrooms, tryin to cram crystal-types and all-else into tiny margins.
That's still a memorable icon for many, (especially to the valence-challenged who still flee that hoary apparition.)

A simply bitchin compilation of stuff which ought to remain There: available but not wasting neuronal storage in overburdened wetware-of-Meat. I wot.
Add a chart of the nuclides (still updated weekly?) and ya gots a Start on how quickly simple-stuff ... Isn't.
Love/Hate It or.. leave.

(Me punts on forced-Boolean choices.)