Really? Another catch-'em game? This doesn't even have the player learning about the chemicals. You just start with noble gasses, and work your way around. Seriously weak. It's not educational about chemistry at all, and isn't even that fun. Who chose the circus music for your title? No cookie for them!

Needs more levels, and more items to interact with. But it´s a nice start.

This is a cute game but needs more game elements. It's a chemistry game but their don't seem to be any reactions like nitrogen and water to create fog or tin and sulfur to make hydrogen for a balloon so your character can float around, you can even use charged noble elements to make colorful lights. The game needs more things to reword the player. As for a game ender why not make that a simple death mix like a cute explosion, fire or deadly gas?

I'm with the others who suggested growth/shrinking, or perhaps a bonus of fast or a penalty of slow for catching the right or wrong things respectively.

The idea is okay, but the gases were sort of tedious and too long. Plus I had like 18 lives XD? ThaT's a little much. The H was just... Well collecting only that one thing o.0?
You should maybe include some eh additional stuff? Like maybe shrinking/growth so it'll be easier/harder to avoid or maybe a speed powerup?