A couple of days ago, Laura mentioned on Twitter that the periodic table has changed a lot since she studied it at school. I started to think about that and remembered that the layout from Mendeleev had gaps for the elements yet to be discovered, so it would be interesting to see how those gaps have been filled.

After a quick search I found a table with the list of the discoveries of the elements, and it seemed to be a good excuse to learn D3. I then started to work on a quick visualization project. The goal was to show how the table has changed since it was developed and to be able to find patterns in the discoveries. For example, I noticed that about half of the elements were already known when Mendeleev presented his table in 1869, and almost all the noble gases were observed for the first time in the 1890s.

Also, it looks like there are 3 periods where most of the discoveries happened: around 1800, between 1875 and 1900, and from 1940 to 1960 (after almost 25 years of no discoveries). I have no idea if there’s an explanation for that, though.

Anyway, although the visualization is quite simple, I’m happy with it: