What is the definetion for elements?

Answer 1

An element is any substance that has only one type of atom in it (e.g. aluminium atoms). Every known element is presented on the Periodic Table of the Elements and classified into groups and periods. Some of the elements either never did or don't now naturally occur, and so scientists must synthesise them.

Answer 2

Elements are pure substances that cannot be broken down into simpler substances by chemical means. Each element is uniquely defined by the number of protons in the nucleus of its atoms, which determines its chemical properties. The periodic table organizes elements based on their atomic number and properties.