sumo#elemental_substance  pure_substances that cannot be separated into two or more substances by ordinary chemical (or physical) means; this excludes nuclear reactions; elemental_substances are composed of only one kind of atom, e.g., iron (Fe), copper (Cu), and oxygen (O_2); elemental_substances are the simplest pure_substances
  closed_exclusion:  compound_substance
  supertype:  pure_substance  substances with constant composition, e.g., table salt, sugar, water, iron, copper and oxygen
  subtype:  metal  an elemental_substance that conducts heat and electricity, is shiny and reflects many colors of light, and can be hammered into sheets or drawn into wire; about 80% of the known chemical elements (sumo#elemental_substances) are metals
  subtype:  atom  an extremely small unit of matter that retains its identity in Chemical reactions; it consists of an atomic_nucleus and electrons surrounding the atomic_nucleus
  subtype:  subatomic_particle__subatomicparticle  the class of elemental_substances that are smaller than atoms and compose atoms
     subtype:  atomic_nucleus  the core of the atom; it is composed of protons and neutrons
     subtype:  electron  sumo#subatomic_particles that surround the atomic_nucleus; they have a negative charge
     subtype:  proton  components of the atomic_nucleus; they have a positive charge
     subtype:  neutron  components of the atomic_nucleus; they have no charge

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