The correct answer is option 2, Diamond.

An element is a pure substance that cannot be broken down into simpler substances by chemical means. It consists of only one type of atom. In this case, diamond is an element because it is composed entirely of carbon atoms arranged in a specific crystal structure.

Now let`s analyze the other options provided:

- Option 1, Topaz, is not an element. It is a mineral composed of aluminum, silicon, and fluorine.

- Option 3, Ruby, is also not an element. It is a gemstone made of the mineral corundum, which is primarily composed of aluminum oxide.

- Option 4, Sapphire, is another gemstone made of the mineral corundum. It is also not an element because it is composed of aluminum oxide.

Therefore, the only correct answer among the given options that represents an element is option 2, Diamond.