Particles

In an atom, electrons are attracted to the nucleus by the electromagnetic force.  The electromagnetic force is 10^39 times stronger than the gravitational attraction between them.  The electromagnetic repulsion between proton in the nucleus is overcome by the strong nucleus force.  But when the nucleus becomes too big, the electromagnetic repulsion will have the upper hand and the nucleus will split up to smaller nuclei.

Nucleus of an atom is composed on particles called nucleons - protons and neutrons.  Nucleon is a type of hadrons (Greek word for large).  Hadrons are particles that feel the strong nuclear force.  There are 2 subgroups.  The first group called baryons which comprises proton, neutron, Lambda, Sigma, Xi and Omega.  The other group called mesons comprises pion and other more massive particles such as eta and kaon.  Hadrons are built from quarks.

There are 6 types of quarks, each with a different mass.  Three of the quarks (down/strange/bottom) carry negative charge which is 1/3 of an electron.  The other 3 (up/charm/top) carry positive charge which is 2/3 of a proton.  Each quark actually made up of 3 particles called - red, green and blue.

Proton is made up of 3 quarks - 2 up (2/3 positive charge) and 1 down (1/3 negative charge).  Neutron is made up of 2 down and 1 up quarks.

The other 4 flavor of quarks are "strange", "charm", "top" and "bottom".

The quarks have quantum properties - mass, electrical charge and spin.  Quarks also carry a color charges that is used to explain the formation of nucleons, pion and the relative masons.  Color changes is related to the strong nuclear force.

Spin property is not actual motion.  It means that the particles react to others as if it is rotating in certain way.  Particles that have an integer value of spin (0, 1, 2 etc) are called bosons.  Particles with half spin value (1/2, 3/2 etc) are called fermions

Bosons are carriers of forces.  There are 5 fundamental bosons:

• photon (electromagnetism), spin = 1
• gluon (strong nuclear force), spin = -1
• Z boson (weak nuclear force), spin = -1
• W boson (weak nuclear force), spin = -1
• Higgs boson, spin = 0
• graviton, spin = 2

Fermions form matter.  Quarks are fermions.  The other only elementary particles are leptons (Greek word for small).  Leptons are particles that does not feel the strong nuclear force, basically everything that is not quarks.   Leptons comprises electrons and its heavier relatives - muons and tau, and the 3 types of chargeless and lighter neutrinos - electron neutrino, muon neutrino and tau neutrino. Leptons are elementary particles that cannot be further broken down into smaller parts.

Leptons are classified into 3 generations (based on the sequence of discovery?).  Electron and the electron neutrino are called the first generation (family).  The muon and the muon neutrino are called second generation.  Tau and tau neutino are called the third generation

When a neutron decays to a proton and electron, the resulting mass is smaller than the original neutron.  The remaining mass forms into a neutrino (Italian word means the smaller neutral one).

Tachyons are particles that travels faster than the speed of light.