Tom’s Infinite Science Archive: Atomic Physics - Atom & Atomic Theory The Standard Model Color Charge & Confinement Antimatter

Helpful Information -

Definition:
Concerned with the structure and properties of the atom.

Elementary Particle:

Any of the subatomic particles that compose matter and energy, especially one hypothesized or regarded as an irreducible constituent of matter. Also called fundamental particle.

Introduction

Elementary Particles, smallest units of matter, with diameters in the range of approximately 10-13 to 10-16 cm [approximately 4 × 10-14 to 4 × 10-17 in]. Elementary particle physics-the study of elementary particles and their interactions-is also called high-energy physics, because the energy involved in such dimensions is very high, as the uncertainty principle dictates [see Quantum Theory]. The term elementary particle was originally ascribed to the constituents of matter in these extremely small spatial dimensions because they were thought to be indivisible. Most of them are now known to be highly complex, but the name elementary particle is still applied to them.

Classification

Several hundred elementary particles are now known experimentally through the various properties by which physicists identify them. They are divided into four broad classes- the photon, the leptons, the baryons and the mesons. Examples are listed in the accompanying table.

Protons and neutrons are the basic constituents of atomic nuclei, which, combined with electrons, form atoms. Photons are the fundamental units of electromagnetic radiation, which includes radio waves, visible light, and X rays. The neutron is unstable as an isolated particle, with an average life of 917 seconds. When combined with protons, however, to form certain atomic nuclei, such as oxygen-16 or iron-56, the neutrons are stabilized. Most of the elementary particles other than the electron, photon, proton, and neutron have been discovered since 1945, some in cosmic rays, the remainder in experiments using high-energy accelerators [see Particle Accelerators]. The existence of other particles has been predicted, but they have not yet been observed-such as the graviton, thought to transmit the gravitational force.

Some elementary particles, such as the photon, are their own antiparticles. Physicists generally use a bar to denote an antiparticle; thus e is the antiparticle of e^-.

Particles may also be classified in terms of their spin, or angular momentum, as bosons or fermions [see Fermion]. Bosons have a spin that is a whole-integer multiple of a certain constant, h; fermions have a spin that is a half-integer multiple of that constant.

Subatomic Particle:

Any of various units of matter below the size of an atom, including the elementary particles and hadrons. Subatomic particles are the basic units of all matter and energy. Many subatomic particles have been identified, but there are four main types: photons, leptons, mesons, and baryons.

This site contains the following references & information:

Photons, which are specific subatomic particles that are units of light or of electromagnetic energy, [see Photon, Antimatter, Elementary Particles: Classification]

Leptons, which are relatively small subatomic particles that are neutral or have a unit charge, [see Lepton, Atom and Atomic Theory: Elementary Particles]

Large class of elementary particles that includes mesons and baryons, [see Hadron]

Mesons, which include the lighter kaon and pion particles, [see Hadron, Atom and Atomic Theory: Elementary Particles, Elementary Particles: Classification]

Baryons, which are a class of the heaviest elementary particles, including nucleons and heavier, unstable hyperons, [see Baryon, Hadron, Neutron, Proton]

Basic particle that makes up mesons and baryons, [see Quark]

Subatomic particles that hold quarks together, [see Gluon, Quantum Chromodynamics]

Particles that have been predicted to exist but have not yet actually been observed, including the graviton, [see Elementary Particles: Classification]

Quantum theory as a replacement for Newton's laws in dealing with subatomic particles, [see Quantum Theory: Early History]

Place of subatomic particles in the origin of the universe and in other cosmological phenomena, [see Cosmic Rays: Introduction, The Big Bang Theory - Coming soon, Dark Matter - Coming soon]

Spin as a property of subatomic particles, [see Electron]

Measurement of subatomic particles, [see Electron Volt, Molecular Theories - Coming soon]

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Quite often, physicists want to study massive, unstable particles that have only a fleeting existence (such as the very massive top quark.) However, all that physicists have around them in the every day world are very low-mass particles. How does one perform this amazing feat of using particles with lesser mass to obtain particles of greater mass?

You know Albert Einstein's famous equation: E=mc² where E is the energy, m is the mass, and c is the speed of light. Therefore,

When a physicist wants to use particles with low mass to produce particles with greater mass, all she has to do is put the low-mass particles into an accelerator, give them a lot of kinetic energy (speed), and then collide them together. During this collision, the particle's kinetic energy is converted into the formation of new massive particles. It is through this process that we can create massive unstable particles and study their properties.

As physicists kept discovering more and more particles all the time. They have discovered about 200 particles (most of which are not fundamental.) They had to decide on a naming convention to keep track of all these particles. To this end, they assigned letters from the Greek and Roman alphabets to individual particles.
Since you already know how to pronounce the Roman (our) alphabet, here's a pronunciation guide to the Greek alphabet:

Uncial, Miniscule

Elgish Name (pronunciation)

A, a	Alpha (AL-fuh)
B, b	Beta (BAY-duh)
G, g	Gamma (GAMM-uh)
D, d	Delta (DEL-tuh)
E, e	Epsilon (EP-si-lahn)
Z, z	Zeta (ZAY-duh)
H, h	Eta (AY-duh)
Q, q	Theta (THAY-duh)
I, i	Iota (eye-O-duh)
K, k	Kappa (KAP-uh)
L, l	Lambda (LAM-duh)
M, m	Mu (Mew)
N, n	Nu (New)
X, x	Xi (Zee or Z-eye)
O, o	Omicron (O-mi-crahn)
P, p	Pi (Pie)
R, r	Rho (Row)
S, s	Sigma (SIG-muh)
T, t	Tau (T-awe or T-ow like "owl")
U, u	Upsilon (OOP-si-lahn or UP-si-lahn)
F, f	Phi (F-eye)
C, c	Chi (K-eye)
Y, y	Psi (Sigh)
W, w	Omega (oh-MAY-guh)

Many particle names are more complex words. Here is a handy pronunciation guide to particle names:

Particle Pronunciation Guide For each of the matter particles, there is a corresponding antimatter particle. baryon: BARE-ee-on boson: BOZE-on electron: e-LEC-tron (e-) fermion: FARE-mee-on gluon: GLUE-on hadron: HAD-ron kaon: KAY-on (K) lepton: LEP-tahn meson: MEZ-on muon: MEW-on (µ) neutrino: new-TREE-no () neutron: NEW-tron (n) nuclear: NEW-klee-er nucleus: NEW-klee-us nucleon: NEW-klee-on photon: FOE-tahn () pion: PIE-on () positron: PAUSE-i-tron (e+) proton: PRO-tahn (p) quark: KWORK (q) tau: TAOW ()

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