What is an element?

An element is a ‘pure substance’ consisting of atoms of the same kind. Elements cannot be broken down into simpler substances, but they can combine with other elements to make new substances. Each element has a unique symbol, for example, ‘O’ means oxygen, ‘Na’ means sodium (Latin: natrium), and ‘CI’ means chlorine. The number of protons in the atomic nucleus determines the element. This number is called the atomic number of the element.