The strong and weak nuclear forces? Electron shielding? Gluon attraction? Too bad Physicist isn't here, I'm in over my head..
Physicist could answer this far better than I; but here goes:
THE STANDARD MODEL:
The best description of how matter and energy interact (sans gravity) is called “The Standard Model” It describes the organization of all of the particles and how they interact. The elementary particles are divided into two families called quarks and leptons. Each family consists of six particles and three of each particles in each group are acted on by a force carrier.
Quarks: Six called, up charm, top, down, strange, and bottom.
Up, charm, and top use the gluon for their force carrier.
Down, strange, and bottom use the photon for their force carrier.
Leptons: Six called: e neutrino, u neutrino, t neutrino, electron, muon, and tau.
E neutrino, u neutrino, and t neutrino use the W boson for their force carrier.
Electron, muon, and tau use the Z boson for their force carrier.
Gravity is not included in the standard model, however it is believed that is exchange force is a graviton.
THE FOUR FUNDEMENTAL FORCES OF NATURE:
The four fundamental forces in nature:
Strong force
Weak force
Electromagnetism (EM)
Gravity
All of the fundamental forces are considered Exchange Forces. In other words the force involves an exchange of one or more particles.
The exchange particles are as follows:
Strong – The pion (and others)
Electromagnetic (EM) – The photon
Weak – The W and Z
Gravity – The graviton
The Strong Force:
It is a force that holds the nucleus together against the repulsion of the Protons. It is not an inverse square force like EM and has a very short range. It is the strongest of the fundamental forces.
The Weak Force:
The weak force is the force that induces beta decay via interaction with neutrinos. Not only would the Sun not burn without this force A star can “burn” by a nuclear fusion process. Three of those processes are proton-to proton fusion, helium fusion, and the carbon cycle. Here is an example of proton-to-proton fusion, which is the process our own sun uses: (two protons fuse -> via neutrino interaction one of the protons transmutes to a neutron to form deuterium -> combines with another proton to form a helium nuclei -> two helium nuclei fuse releasing alpha particles and two protons). The weak force is also necessary for the formation of the elements above iron. Due to the curve of binding energy (iron has the most tightly bound nucleus), nuclear forces within a star cannot form any element above iron in the periodic table. So it is believed that all higher elements were formed in the vast energies of supernovae. In this explosion large fluxes of energetic neutrons are produced which produce the heavier elements by nuclei bombardment. This process could not take place without neutrino involvement and the weak force.
Electromagnetism:
The electromagnetic force is the forces between charges (Coulomb’ Law) and the magnetic force which both are describe within the Lorentz Force Law. Electric and magnetic forces are manifestations of the exchange of photons. A photon is a quantum particle of light (electromagnetic radiation). This particle has a zero rest mass, however, light has relativistic mass (since its traveling at the speed of light “C”) and can be acted on by gravity. The speed of light in a vacuum is a constant and is unobtainable by matter due to the lorentz transformation. Electromagnetism obeys the “inverse square law”.
Gravity:
Gravity is the weakest of the forces and also obeys the inverse square law. The force is only attractive and is a force between any two masses. Gravity is what holds and forms the large scale structures of the universe such as galaxies.