A material that is made up of only one kind of atom is called a chemical element, a basic element or simply an element. Elements are pure chemical substances distinguished by a unique atomic number.
The atomic number is defined as the number of protons in its atomic nucleus. The periodic table of elements is a tabular arrangement of the chemical elements in which elements are arranged by order of atomic number, electron configuration and recurring chemical properties. Elements are divided into metals, metalloids and non-metals. Examples of some common elements are hydrogen, oxygen, nitrogen, gold, copper, iron and lead.