Medical Definition of Atom

  • Medical Author:
    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Reviewed on 12/27/2018

Atom: The smallest part of any material that cannot be broken up by chemical means. Each atom has a center (the nucleus) which contains protons and neutrons. Electrons orbit around the nucleus. The atom is primarily empty space.

If the nucleus of an atom were the size of the button on a baseball pitcher's cap, the electrons would be like dust particles revolving around the outside of the baseball stadium.

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Reviewed on 12/27/2018