Element

Summary: A pure substance made of only one type of atom. Cannot be broken down into simpler substances by chemical means. Tags: igcse chemistry definition atomic-structure Created: 2026-07-14 Last Updated: 2026-07-14

An element is a pure chemical substance consisting entirely of atoms that all have the same atomic number — that is, the same number of protons in their nucleus — and therefore the same chemical identity. The approximately 118 known elements are organised in the Periodic Table in order of increasing atomic number, arranged into groups (vertical columns) and periods (horizontal rows) that reflect recurring patterns in their physical and chemical properties. Each element is represented by a unique one- or two-letter chemical symbol derived from its English or Latin name, such as Na for sodium (from natrium) or Fe for iron (from ferrum). Because every atom in a sample of an element has the same number of protons, elements cannot be broken down into simpler substances by any chemical reaction, although nuclear reactions can transmute one element into another. IGCSE students are expected to understand that elements are the fundamental building blocks of all matter and to be able to classify an element as a metal or non-metal based on its position in the Periodic Table and its characteristic properties.

Key term — IGCSE Chemistry (0620/0971) glossary.