What distinguishes an element from a compound?

An element is a pure substance made of identical atoms, while a compound is a substance made of two or more different elements chemically combined.

An element is the simplest form of matter that cannot be broken down into simpler substances by any chemical means. It is a pure substance made up of identical atoms. For example, gold, silver, and oxygen are all elements. Each element is represented by a unique symbol in the periodic table and is characterised by a specific number of protons in its nucleus, known as its atomic number. Elements can exist in different physical states - solid, liquid, or gas - and can combine with other elements to form compounds.

On the other hand, a compound is a substance that is formed when two or more different elements combine chemically in a fixed ratio. The properties of a compound are usually different from the properties of the elements that make it up. For instance, water is a compound made up of hydrogen and oxygen. While hydrogen is a highly flammable gas and oxygen supports combustion, water is a liquid that is used to extinguish fires. Compounds are represented by chemical formulas that indicate the types and numbers of atoms involved.

In summary, the key difference between an element and a compound lies in their composition. An element is a pure substance made up of identical atoms, while a compound is a substance that is formed when two or more different elements combine chemically. Understanding this distinction is fundamental to the study of chemistry.