Chemistry For Dummies
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Chemistry deals with atoms, which are composed of subatomic particles that differ in mass and charge. Altering the numbers of these particles can alter the element or the isotope identity of an atom. Here are some subatomic facts:

  • Subatomic particles:

    • Proton, p+: 1 atomic mass unit (amu), +1 charge

    • Electron, e: 1/1,836 amu, –1 charge

    • Neutron, n0: 1 amu, 0 charge

  • Atomic number:

    • Equals the number of protons

    • Determines the element

  • Mass number:

    • Equals the number of protons plus neutrons

    • Determines the isotope

About This Article

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About the book author:

John T. Moore, EdD, is Regents Professor of Chemistry Emeritus and Coordinator of STEM Activities at Stephen F. Austin State University. He is the author of Chemistry For Dummies and coauthor of Biochemistry For Dummies.

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