I like that you've chosen to use an actual element for the example / explainer.

To streamline the UI, might I suggest replacing example element (copper) with just the explainers, next to hydrogen [2]... using that elements information (without adding a free-floating copper).

If that doesn't make sense, let me know.

Thanks for being a responsive educator.

[2] perhaps use Beryllium for your example/explainer -- because then you can explain the electron orbitals too ..?

----

Replace the topbar (color==atomic class) location to between Group II & III elements (e.g. whitespace between Be B); does not need to be explained on example element text.