I recently played Sokobond and completed all the 100+ puzzles. It was quite all right. Some may consider the price tag a bit high for how simple the game looks, but I found it worth it because the puzzles were well designed and got harder towards the end.
What is it about? Well, you are an atom. You get to move on a square grid and push other atoms around, which makes up for the Sokoban-like part of the game. You will also make the atoms bond with other atoms by moving them to adjacent squares, if they have available electrons for bonding. The goal is to make complete molecules without any free electrons. You cannot rotate anything and you need to mind narrow corridors and other obstacles to avoid getting your incomplete molecules irretrievably stuck. (There is unlimited undo.)
Mind you that because all this happens on a square grid and it doesn't go into the details, it's not really a game with actual chemistry in it. You get only five different kinds of atoms that have from zero to four possible bonds. The game starts with easy intro puzzles, but as the game progresses you have more choices for what to try next.
There are a few other interactions that the game adds on later levels that make for more complex puzzles. Overall it's just this one basic puzzle idea, but executed solidly. I enjoyed playing it. There is maybe 10 to 15 hours of puzzle solving for someone fairly good at puzzles, if I may rank myself as one. It'll take less if you don't get stuck as often as I did
(Actual listed time I had the game open: 13h 31m. It includes a nap.)
I have the Gog.com version. I suppose the one on Steam is the same and has some Steam achievements in addition. Right now GOG is showing me a lower local price in Euros, so make sure to compare your prices too.
https://www.gog.com/game/sokobond
http://store.steampowered.com/app/290260/Sokobond/
(I did a search for Sokobond before posting, so I believe no one has mentioned this before. I vaguely remember a similar free game that came pre-installed in some Linux distro years ago, but I have forgotten its name. I'm pretty sure it had atoms and bonding too.)