I have to admit that I hadn’t fully grasped the differences between these two. So I’m guessing lots of other people hadn’t done either. And the dictionary is quite opaque on this, talking about chemical compounds rather than the essential, understandable differences, although my trusty “New Oxford Style Manual” does better.
Silicon is a naturally occurring element (symbol Si) which is hard and durable and used in the silicon chips inside computers.
Silicone is a synthetic compound of silicon, and this is the one that’s used in breast implants and cooking utensils: it can be a liquid or gel as well as a solid.
So, actually two that it’s a good idea NOT to get mixed up!
You can find more troublesome pairs here and the index to them all so far is here.