The smallest particle of an element that retains the chemical properties of an element.

Atoms are normally electrically neutral, with a positively charged nucleus that binds one or more electrons in motion around it. Electrically charged atoms are known as ions. Atoms group together to form molecules. Nanotechnology — especially mechanosynthesis-based hylonanotech — is the physical manipulation of individual atoms.

Atomic Number: The number of protons in an atomic nucleus.

Atomic Weight: The average mass of an atom of an element, usually expressed in atomic mass units. The atomic weight given on the periodic table is the average of isotopic masses found in a typical terrestrial sample of the element.

Atomic Nucleus: The tiny, dense positively charged mass at the centre of the atom; composed of protons and neutrons.

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  • Electron - Text by M. Alan Kazlev
    An elementary particle with a unit electrical charge and a mass 1/1837 of the proton. Electrons surround the atom's positively charged nucleus and determine the atom's chemical properties.
  • Element - Text by M. Alan Kazlev
    A chemically pure substance composed of atoms of a single type.
  • Exotic Atoms - Text by Stephen Inniss
    A term used for matter that is not composed of the usual protons, neutrons and electrons but that forms analogous structures. The constituent particles of monopolium/magmatter are an example. Some such "atoms" may be said to form "molecules" or analogues of metals or ionic compounds and may be used in the construction of such things as Banks Orbitals.
  • Fermion - Text by M. Alan Kazlev
    Subatomic particle with half integer spin. The Pauli Exclusion Principle prevents more than one fermion occupying a particular quantum state. This means matter is conserved during particle interactions (i.e. that the net amount of fermions is a constant). The electron is considered a typical fermion, and it is because of its half-spin quality that electrons form into "shells" providing the outer valence electrons that make chemistry work, as well as making life and atoms as we know them possible. Contrast with the boson. [after physicist Enrico Fermi]
  • Hadron - Text by Anders Sandberg
    Matter particle consisting of quarks or antiquarks. Hadrons are divided into mesons, composed of a quark and an antiquark, and baryons, composed of three quarks or three antiquarks.
  • Molecule
  • Neutrino - Text by M. Alan Kazlev; additions by Adam Getchell
    An electrically neutral lepton of spin 1/2 and extremely low mass that interacts only via the weak force and gravity and as a consequence can typically pass unimpeded through ordinary matter. A common popular illustration of this is that a burst of neutrinos could pass through a light year's thickness of lead and still retain better than two thirds of its strength. There are three known varieties in conventional matter, one in each generation of particles, associated with electron, muon, and tau leptons.
  • Neutron - Text by M. Alan Kazlev
    Uncharged atomic nuclear particle. It has a mass slightly greater than a proton. In beta decay, a neutron decays into a proton, an electron, and an anti-neutrino.
  • Proton - Text by M. Alan Kazlev
    One of the two basic elementary particles found the atomic nucleus, the other being the neutron. It has a positive charge equal and opposite that of the electron, and a mass similar to the neutron. Protons have a mass of 1.007276 daltons, or 1.6726 = 10-27 kg.
  • Quark - Text by M. Alan Kazlev
    The fundamental particles of hadronic matter such as protons, neutrons and mesons. There exist six 'flavors' of quarks: up, down, strange, charm, top and bottom. They are confined to hadrons by the strong force.
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Development Notes
Text by M. Alan Kazlev
Initially published on 07 October 2001.