The physical world is composed of combinations of various subatomic or fundamental particles
. These are the smallest building blocks of matter. All matter except dark matter is made of molecules, which are themselves made of atoms. The atoms consist of two parts. An atomic nucleus
and an electron cloud
. The electrons are spinning around the atomic nucleus. The nucleus itself is generally made of protons and neutrons
but even these are composite objects. Inside the protons and neutrons, we find the quarks
Quarks and electrons are some of the elementary particles. A number of fundamental particles have been discovered in various experiments. So many, that researchers had to organize them, just like Mendeleev did with his periodic table. This is summarized in a theoretical model (concerning the electromagnetic, weak, and strong nuclear interactions) called the Standard Model. In particle physics, an elementary particle or fundamental particle is a particle whose substructure is unknown, thus it is unknown whether it is composed of other particles. Known elementary particles include the fundamental fermions and the fundamental bosons.
See also: Baryons
See also: Leptons
The fermions are generally “matter particles” and “antimatter particles”:
The quarks combine to form composite particles called hadrons, the best known and most stable are protons and neutrons.
For every quark there is a corresponding type of antiparticle. The antiquarks have the same mass, mean lifetime, and spin as their respective quarks, but the electric charge and other charges have the opposite sign.
The best known of all leptons are the electrons and the neutrinos
See also: Leptons
For every lepton there is a corresponding type of antiparticle. The best known of all antileptons are the positrons and the antineutrinos.
The bosons are generally “force particles” that mediate interactions among fermions:
The gauge boson is a force carrier of the fundamental interactions of nature.
The Higgs bosons give other particles mass via the Higgs mechanism. Their existence was confirmed by CERN on 14 March 2013.
However, only a few of these fundamental particles (in fact, some of these are not fundamental particles – e.i. neutron consist of three quarks) are very important in nuclear engineering. Nuclear engineering or theory of nuclear reactors operates with much better known subatomic particles such as:
The electrons are negatively charged, almost massless particles that nevertheless account for most of the size of the atom. Electrons were discovered by Sir John Joseph Thomson in 1897. Electrons are located in an electron cloud, which is the area surrounding the nucleus of the atom. The electron is only one member of a class of elementary particles, which forms an atom.
The protons are positively charged, massive particles that are located inside the atomic nucleus. Protons were discovered by Ernest Rutherford in the year 1919, when he performed his gold foil experiment.
are located in the nucleus with the protons. Along with protons, they make up almost all of the mass of the atom. Neutrons were discovered by James Chadwick in 1932, when he demonstrated that penetrating radiation incorporated beams of neutral particles.
is an elementary particle, the force carrier for the electromagnetic force. The photon is the quantum of light (discrete bundle of electromagnetic energy). Photons are always in motion and, in a vacuum, have a constant speed of light to all observers (c = 2.998 x 108 m/s
is an elementary particle, one of particles which make up the universe. Neutrinos are electrically neutral, weakly interacting and therefore able to pass through great distances in matter without being affected by it.
Positron is an antiparticle of a negative electron. Positrons, also called positive electron, have a positive electric charge and have the same mass and magnitude of charge as the electron. An annihilation occurs, when a low-energy positron collides with a low-energy electron.