Physicists later discovered matter contains atoms and not these four elements. The word atom stands for smallest particle, and by its name, matter was classified by its atomic structure, the periodic table.

Atoms, as we know, consist of a nucleus with protons and neutrons and electrons surrounding this central core. Thus, the atom is not the smallest particle and is not fundamental. Fundamental means simple and without substructure. Clearly the nucleus has a substructure.

This is not the end though. Protons, neutrons, and many other particles have been discovered to consist of six fundamental elements, called quarks.

 Currently, physicists believe quarks are the fundamental building blocks for matter. Every planet, star, and chair you sit on begins with these building blocks of quarks, which mix together to form these items. So the only fundamental particles are the quarks and the group of particles containing the electron (called the leptons).

The Fundamental Particles: Quarks

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