What makes an element an element? Elements are the purest substances known. Copper is an element. The element copper consists of only copper, which is not combined with anything else. Iron is also an element. Iron is iron and nothing else. Each element is represented by a symbol. The symbol for copper is Cu and the symbol for iron is Fe.

Elements are made up of atoms. Atoms are the simplest building blocks of an element. If you took a block of an element and cut it into smaller and smaller pieces, an atom would be the smallest piece that you could have before you destroyed the element. The atoms of each element are unique and their properties define those of the element. Atoms are incredibly small and have a diameter on the order of 10^-10 m. Millions of atoms make up everything we see.