by Ron Kurtus (19 September 2001)

Although the Proton, Neutron and Electron have been considered the fundamental particles of an atom, recent discoveries from experiments in atomic accelerators have shown that there are actually 12 fundamental particles. They are divided into two classes, consisting of Leptons and Quarks. The proton and neutron are no longer considered fundamental particles in this sub-atomic classification. 

Questions you may have about sub-atomics particles are:

• What are the Leptons?
• What are the Quarks?
• How does this all fit with atomic physics?

Leptons

The Lepton classification of sub-atomic particles consists of 6 fundamental particles:

• Electron
• Muon
• Tau
• Electron Neutrino
• Muon Neutrino
• Tau Neutrino

Electron, Muon and Tau Leptons

The Electron remains a fundamental particle, as if was in the Atomic Theory. It has an electrical charge of (-1) and plays an active role in chemical reactions.

The Muon is primarily a result of a high-energy collusion in an atomic accelerator. The Muon is similar to an Electron, only heavier.

The Tau particle is similar to a Muon, only heavier yet.

Muon and Tau particles are unstable and exist in nature for a very short time.

Neutrinos

Neutrinos are small and have no electrical charge. This makes them extremely difficult to detect. They can possess a large amount of energy and the very rare times they do collide with another particle, that energy can be released.

In central Russian in the early 1900s, "something" exploded, knocking down hundreds of trees in the forest, around a single point. Scientists speculate that this was caused by a speeding Neutrino striking an atom.

The types of neutrinos are:

• Electron Neutrino, which has no charge and is extremely difficult to detect
• Muon Neutrino, which is created when some atomic particles decay
• Tau Neutrino, which is heavier than the Muon Neutrino.

Quarks

Another group of sub-atomic particles are the Quarks. Just like their name, they exhibit unusual characteristics. The fundamental particles among the Quarks are:

• Up and Down Quarks
• Charm, Strange, Top and Bottom Quarks

Other particles are made up of combination of Quarks.

Up and Down Quarks

The Up Quark has an electrical charge of (+2/3). The Down Quark has an electrical charge of (-1/3).

Proton

The Proton is made up of  two Up Quarks and one Down Quark. The electrical charge of the proton is then: (+2/3) + (+2/3) + (-1/3) = (+1).

Neutron

The Neutron is made up of one Up Quark and two Down Quarks. The resulting electrical charge of the Neutron is: (+2/3) + (-1/3) + (-1/3) = (0).

Charm, Strange, Top and Bottom Quarks

The Charm Quark has the same electrical charge as the Up Quark but is heavier. The Top Quark is then heavier than the Charm.

The Strange Quark has the same electrical charge as the Down Quark but is heavier. The Bottom Quark is then heavier than the Strange.

In conclusion

According to Sub-Atomic Theory, the fundamental particles now consist of 6 Lepton particles and 6 Quark particles. Other particles are made up of combination of Quarks. An Electron is still a fundamental particle, but Protons and Neutrons are combinations of Quarks.

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