A3. Beyond the Atom:

Today we know that there is something more fundamental than 'ATOM'.

The word 'fundamental' means: Objects that are simple & structureless - not made of anything smaller.

In physics, Particles that cannot be broken down further or cannot be divisible furthermore is called Elementary Particles. Sometimes it is also called fundamental particles to avoid confusion.

These fundamental particles provide the basic units that make up all 'matter & energy' in the Universe. All matter around us is made of elementary particles. It also helps to determine the four - fundamental forces also.

Beyond the atom: Elementary particles (1)

Before the discovery of the electron by the British Physicist J. J. Thomson in 1897, Physicists believed that the fundamental units of matter were 'ATOM'. But now a days Physicists can't believe that atom is a fundamental particle because they discover that atom is also split into further more particles like - electrons, protons & neutrons.

Electron is one of the fundamental particles because it appears to have no internal structure.Protons & neutrons are not called as fundamental because they are composed of even smaller elementary particles called 'Quark'. Quark is also another fundamental elementary particles in physics.

As far as we know: 'Quarks' & 'Leptons(electron)' are points in geometry. They are not made up of anything else. So called as fundamental particles.

Now come back to our topic:

In universe there are approximately 200 different types of particles. The Standard model describes these particles & its interactions by using 17 - fundamental particles, except Gravity ('graviton' yet not found).

All of these 17 - fundamental particles are classified into two categories: either 'Fermions' (pronounced: FUR-me-onz) or 'Bosons' (pronounced: BO-zonz). In the universe, everything's (matter & energy) are made from these 'fermions' & 'bosons'. Which are also called building block of fundamental particles.

Fundamental 'fermions' (6-quarks & 6-leptons), combine to form protons, neutrons, electron, atom, molecules, people, table, computer etc. While fundamental 'bosons' (gluon, photon, w-boson, z-boson, higgs boson & graviton) carry forces between fermions.

1. Fermions:

                  - obey Pauli exclusive principle (cannot occupy the same place at the same time);  

            - the particle with half integral spin ½, 3/2,............

Quarks & Leptons are the member of fermions. All the known matter particles are composites of quarks & leptons. They are interacts by exchanging forces carrier particle - Bosons.

Both quarks & leptons group - consists of six - particles, which are related in pairs or generations.

Fermions: Quarks & Leptons

The lightest & most stable particles make up the 1^st generation, whereas the heavier & less stable particles belong to the 2^nd & 3^rd generations.

• The 6-Quarks are classified in the three generation as follows: 

  
  
  
                     I.            1^st generation:   up & down quarks;
                  II.            2^nd generation:  charm & strange quarks;
               III.            3^rd generation:   top & bottom quarks.
  
  
  
  
  Quarks are known to combine into triplets & doublets. They are not found to be alone. Physicists have prove that quarks combine to triplets are called 'baryons' & the combine doublets (i.e. quarks & anti-quark) are called 'mesons'. Baryons are found in the nucleus (proton & neutron) called nucleons.

• The 6-Leptons are classified in the three flavors as follows:

  
  
  
                     I.            1^st flavors: electron & electro neutrino;
                  II.            2^nd flavors: muon & muon neutrino;
               III.            3^rd flavors: tau & tau neutrino.
  
  
  The electron, muon & tau all have an electric charge & a sizeable mass, whereas the neutrinos are electrically neutral & have very little mass, So they are exceptionally difficult to detect.
  Leptons do not need to bind to each other. All of the leptons can be found alone (like: electron in atom).

All stable matter in the universe is made from particle that belongs to the 1^st generation. The remaining 4-quarks & 5-leptons are simply large versions (i.e. heavier & less stable) of those three main particles types. But now a day, Particle physicists are still trying to understand the role of the 2^nd & 3^rd generation in nature.

                                                          Video Source: Beyond the atom

 For example: Protons(2-up & 1-down quarks) & Neutrons(1-up & 2-down) are made of 'up' & 'down' quarks. Electron(1-leptons) forms a shell of orbitals. By combinations of these fermions(quarks & leptons) form atom.

Note: Both quarks & leptons (all of these 12 - particles) have antimatter versions, which behaves the same way, but annihilate upon contact with matter converting the mass of both particles into pure energy.

2. Bosons:

    - does not obey Pauli exclusive principle (no problem to occupying the same place at same time);

    - particle with integer spin 0, 1, 2.............

Bosons are the force carrier particles. They act to transmit force between fermions (quarks & leptons). Gluon, Photons, W-boson, Z-boson, Higgs boson & Graviton; these all are 'Bosons'.

In universe (nature) there are 4 - types of fundamental forces named: Strong force, Electromagnetic force, Weak force & Gravity. Three of these fundamental force results from the exchange of force - carrier particles. Gravity is excluded because 'gravitons' have never been observed yet.

Bosons: 4 - fundamental forces

Each fundamental forces have its own corresponding 'Bosons':

• Strong force: carried by 'Gluon', which binds quarks together inside the protons, neutrons; & hold particles together inside the atomic nucleus.

• Electromagnetic force: carried by 'Photons', which governs electron orbits (electron hold together) & chemical process.

• Weak force: carried by the 'W-boson' & 'Z-boson', which playing a role in radioactive decay.

• Gravity force: Although, not yet found the 'Graviton' should be the corresponding force carrying particle of gravity.

• Higgs boson: has yet to be found conclusively in an experiment. The race is on to find the Higgs bosons - the key to "why some particles have mass?"

[ Note: For the discovery of higgs bosons, Nobel Prize in physics 2013 was awarded jointly to Peter W. Higgs & Francois Englert. For more detail: Click here. ]