Here's why:

* Elements are pure substances that cannot be broken down into simpler substances by chemical means (e.g., gold, oxygen).

* Compounds are substances formed by the chemical combination of two or more elements (e.g., water, salt).

Shale is a sedimentary rock composed of various minerals and organic matter. It is formed by the accumulation and compaction of fine-grained sediment, such as clay, silt, and sand.