Physical Systems Inventory: Atoms

Last modified: Thu 4/24/97 1945 PDT


Canon
Terms		 Object Classes Atom; AtomicNucleus; ElectronCloud; Ion; ChemicalElement; PeriodicTable
Instances (none)
Event Classes (none)
Instances (none)

An atom is a Physical Agent which is an aggregate of subatomic particles, specifically of protons, neutrons and electrons. The protons and neutrons congregate in the atomic nucleus, which is surrounded at great relative distance by the electrons in the electron cloud. The aggregate electrical charge of the nucleus (due to positively charged protons) and that of the electron cloud (due to negatively charged electrons) are often equal, the atom has no net charge. By gaining or losing electrons, however, an atom can acquire a positive or negative charge and is then referred to as in ion.

One important classification of atoms is based on the number of protons in the nucleus. A class of atoms having a certain number of protons is called a chemical element. Because numerous characteristics of both atomic structure and behavior are correlated with the number of protons and form systematically recurring patterns, the chemical elements are systematized in what is called the Periodic Table of Chemical Elements.

As composite subatomic particles, atomic nuclei are either fermions or bosons, depending on whether their total number of neutrons and protons is odd or even. This explains, for example, the superfluid behavior of supercooled helium: the atomic nuclei are bosons and can pass through each other.

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Copyright 1997 by Mark P. Line (<waldzell@pair.com>)