#atom  (physics and chemistry) the smallest component of an element having the chemical properties of the element
  supertype:  substance__matter  that which has mass and occupies space; "an atom is the smallest indivisible unit of matter"
  part:  elementary_particle  nucleus
  part of:  chemical_element  molecule
  subtype:  ion  an electrically charged particle; an atom that has lost one or more of its electrons
     subtype:  anion  a negatively charged atom
        subtype:  hydroxide_ion__hydroxideion__hydroxyl_ion  the anion OH having one oxygen and one hydrogen atom
        subtype:  superoxide_anion__superoxide  the univalent anion O2-; "much of the O2 supporting cellular respiration is reduced to the superoxide anion O2-"
     subtype:  cation  a positively charged atom
        subtype:  hydrogen_ion  a positively charged atom of hydrogen; that is to say, a normal hydrogen atomic nucleus
        subtype:  diazonium  the univalent cation R-N:N- (where R is an aromatic hydrocarbon); found in salts that are used in manufacturing azo dyes
     subtype:  ammonium_ion__ammonium  the ion NH4 derived from ammonia; behaves in many respects like an alkali metal ion
     subtype:  calcium_ion__calciumion__factor_IV  ion of calcium; a factor in the clotting of blood
  subtype:  isotope  one of two or more atoms with the same atomic number but with different numbers of neutrons
     subtype:  radioisotope  a radioactive isotope of an element; produced either naturally or artificially
        subtype:  tracer  (radiology) any radioactive isotope introduced into the body to study metabolism or other biological processes
        subtype:  label.radioisotope  a radioactive isotope that is used in a compound in order to trace the mechanism of a chemical reaction
        subtype:  iodine-131  heavy radioactive isotope of iodine with a half-life of 8 days; used in a sodium salt to diagnose thyroid disease and to treat goiter
        subtype:  iodine-125  light radioactive isotope of iodine with a half-life of 60 days; used as a tracer in thyroid studies and as a treatment for hyperthyroidism
     subtype:  deuterium__heavy_hydrogen__heavyhydrogen  an isotope of hydrogen which has one neutron (as opposed to zero neutrons in hydrogen)
  subtype:  monad  an atom having a valence of one
  subtype:  carbon_atom  an atom of carbon
  subtype:  hydrogen_atom  an atom of hydrogen
     subtype:  acidic_hydrogen__acid_hydrogen  a hydrogen atom in an acid that forms a positive ion when the acid dissociates
     subtype:  deuterium__heavy_hydrogen__heavyhydrogen  an isotope of hydrogen which has one neutron (as opposed to zero neutrons in hydrogen)
  subtype:  free_radical__radical  an atom or group of atoms with at least one unpaired electron; in the body it is usually an oxygen molecule than has lost an electron and will stabilize itself by stealing an electron from a nearby molecule; "in the body free radicals are high-energy particles that ricochet wildly and damage cells"

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