Elements in the periodic table are arranged in order of increasing atomic number. The atomic number represents the number of protons in an atom's nucleus, uniquely identifying each element.

The heaviest element in the Periodic Table, which is Oganesson, has 118 protons. Protons are not elementary particles; they're actually made up of even smaller particles called quarks.

The finding could be put to use at a new facility opening in 2020 that might create new elements—that is, nuclei with more than 118 protons—in addition to new isotopes of the known elements ...

It says something about Dmitri Mendeleev that he had an easier time keeping track of the number of protons in the nucleus of an atom than the number of brothers and sisters living under his roof ...