Nice update Wunoumenal!
Here are my suggestions for further development of this game:
1. Enable selling atoms from your inventory.
2. Make it so that you get less money for killing enemies and add more rounds.
3.Nerf the isotope of bromine, seriously radiation for half the track! that should be uranium.
3. To the atom icon in the shop and the inventory add the atomic number, atomic mass end electronegativity. (I just think it would look cool.) If you do this put the price of the atom like on the right of the icon (and maybe in a different color) so the numbers don't get confusing.
4.If you alreadey have a compound like H2 make it so that you can add atoms to it Like H2 + S ---> H2S, or H2 + O --->H2O
5.Well obviously MORE atoms and MORE compounds ;)
6.In the future add more maps and difficulties that alter the price of towers speed of enemies etc.
For now I didnt find any bugs so well done. And sorry for making you read this long essay that makes you realise only how much more work you have to do ;) Good luck.