What is the difference between atoms and elements?
Get ready for an imperfect analogy.
Imagine going to an ice cream store. Let's say that they have 30 different flavors of ice cream. Those are elements, the things that I have available to build my dessert from. The smallest amount of ice cream that the store will sell to me is a scoop. This is an atom. If I want, I can put two or more scoops of ice cream together. This is a molecule. If my molecule has more than one flavor of ice cream, I can call it a compound.
So, in summary:
element - a basic substance that can't be simplified (hydrogen, oxygen, gold, etc...)
atom - the smallest amount of an element
molecule - two or more atoms that are chemically joined together (H2, O2, H2O, etc...)
compound - a molecule that contains more than one element (H2O, C6H12O6, etc...)
What's wrong with the ice cream analogy? Splitting an atom creates different elements (split an oxygen atom and you don't have oxygen any longer). Splitting a scoop of ice cream results in smaller blobs of the same flavor. For the analogy to hold true, the flavor of the ice cream would have to change when you split a scoop (the chocolate 'element' would have to change into some other 'element' (flavor)).