What is the difference between an element and a compound?

An element is a pure substance consisting of only one type of atom, characterized by its specific number of protons in the nucleus, known as the atomic number. Elements cannot be broken down into simpler substances by chemical means. Examples include oxygen (O), hydrogen (H), and gold (Au).

A compound, on the other hand, is a substance formed when two or more different types of atoms chemically bond together in fixed proportions. Compounds have distinct properties that are different from the individual elements that compose them. They can be broken down into simpler substances through chemical reactions. Examples include water (H₂O), carbon dioxide (CO₂), and sodium chloride (NaCl).

In summary, the key difference is that elements are pure substances with only one type of atom, while compounds are made up of two or more different types of atoms chemically bonded together.