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In the 1970's, scientists constructed a theory called the standard model. The atandard model completes the picture of the atom because it describes particles and forces that reside deep within the atom's nucleus. These particles and forces were postulated to account for observations that were made through the use of very high-energy particle accelerators.

The Standard Model

The standard model is a theory that explains the combinations of fundamental particles and fundamental forces that make up all matter.

There are twelve constituents within the standard model.

Three of constituents are the basis for the structure of the material world, as we know it. These three constituents are the up quark, the down quark, and the electron; that's all it takes to make up the proton, the neutron, and the electron.

However, more is needed in order to account for:

  • Neutrinos, which are needed to construct elements heavier than hydrogen,
  • Photons, which mediate electromagnetic forces, and
  • Pions, which are responsible for nuclear stability.

The standard model theory describes all interactions between the fundamental particles (quarks and leptons) and the fundamental force carriers (bosons).