A chemical element is a type of atom that is distinguished by its atomic number; that is, by the number of protons in its nucleus.
Common examples of elements, also shown in peridic table, are hydrogen, carbon, nitrogen, and oxygen.
Elements with atomic numbers 83 or higher (bismuth and above) are inherently unstable, and undergo radioactive decay. Of the first 82 elements, 80 have stable isotopes.
All chemical matter consists of these elements. New elements of higher atomic number are discovered from time to time, as products of artificial nuclear reactions.