Here's why:

* Elements are pure substances that cannot be broken down into simpler substances by chemical means. Beryllium (Be) is a chemical element with atomic number 4.

* Compounds are formed when two or more elements chemically combine in a fixed ratio. For example, beryllium oxide (BeO) is a compound.

* Mixtures are combinations of two or more substances that are not chemically bonded. They can be separated by physical means.

So, while beryllium can form compounds, it itself is a pure element.