What's this?

I needed to practice my periodic table of elements knowledge. I had to learn two things: how to know an element's position based on its atomic number and how to know an element's atomic number based on its position. My first thought was to just pick up some random elements from the periodic table, which would take me a couple of minutes. Instead, I wound up programming a whole website to do it, which took me a little more :)

Data from Periodic Table JSON