Elementary Particles. Particle physics. Subatomic particles[edit] Modern particle physics research is focused on subatomic particles, including atomic constituents such as electrons, protons, and neutrons (protons and neutrons are composite particles called baryons, made of quarks), produced by radioactive and scattering processes, such as photons, neutrinos, and muons, as well as a wide range of exotic particles.
Dynamics of particles is also governed by quantum mechanics; they exhibit wave–particle duality, displaying particle-like behavior under certain experimental conditions and wave-like behavior in others. In more technical terms, they are described by quantum state vectors in a Hilbert space, which is also treated in quantum field theory. Following the convention of particle physicists, the term elementary particles is applied to those particles that are, according to current understanding, presumed to be indivisible and not composed of other particles.[1]
Subatomic particle. In the physical sciences, subatomic particles are particles smaller than atoms.[1] (although some subatomic particles have mass greater than some atoms).
There are two types of subatomic particles: elementary particles, which according to current theories are not made of other particles; and composite particles.[2] Particle physics and nuclear physics study these particles and how they interact.[3] In particle physics, the concept of a particle is one of several concepts inherited from classical physics. But it also reflects the modern understanding that at the quantum scale matter and energy behave very differently from what much of everyday experience would lead us to expect. Interactions of particles in the framework of quantum field theory are understood as creation and annihilation of quanta of corresponding fundamental interactions. This blends particle physics with field theory. Classification[edit] By statistics[edit] Atom. The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons.
The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons (except in the case of hydrogen-1, which is the only stable nuclide with no neutrons). The electrons of an atom are bound to the nucleus by the electromagnetic force. Likewise, a group of atoms can remain bound to each other by chemical bonds based on the same force, forming a molecule.
An atom containing an equal number of protons and electrons is electrically neutral, otherwise it is positively or negatively charged and is known as an ion. An atom is classified according to the number of protons and neutrons in its nucleus: the number of protons determines the chemical element, and the number of neutrons determines the isotope of the element.[1] Etymology History of atomic theory Atomism First evidence-based theory The structure of atoms The physicist J.
Structure. Particle. Conceptual properties[edit] Treatment of large numbers of particles is the realm of statistical physics.[6] When studied in the context of an extremely small scale, quantum mechanics becomes important and gives rise to several phenomena demonstrated in the particle in a box model[7][8] including wave–particle duality,[9][10] or theoretical considerations, such a whether particles can be considered distinct or identical.[11][12] Size[edit] Galaxies are so large that stars can be considered particles relative to them The term "particle" is usually applied differently to three classes of sizes.
The term macroscopic particle, usually refers to particles much larger than atoms and molecules. Composition[edit] Particles can also be classified according to composition. Stability[edit] Both elementary (such as muons) and composite particles (such as Sigma baryons), are known to undergo particle decay. N-body simulation[edit] N refers to the number of particles considered. See also[edit]