In what two ways can elements occur in nature?
As the pure element (or as an elemental mixture), or chemically bound to other elements in a compound.
Some few elements occur naturally in their elemental form: examples include carbon (as coal or as diamond) as well as elemental gold in nuggets. Gases found in the atmosphere occur as an elemental mixture: mostly dinitrogen and dioxygen, which we are breathing right now. Of course, most elements are found as constituents in chemical compounds: for instance as carbon dioxide in the atmosphere, or as silicates in the soil - oxygen compounds are very common.