3.3: Atomic Weight
- Page ID
- 55486
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Protons and neutrons have weight (mass), whereas electrons, for all practical purposes, do not. Neutrons and protons weigh about the same; their numbers in an atom determine its atomic weight. The actual weights of atoms are infinitesimally small, so atomic weights are given as relative weights—relative to carbon having an atomic weight of 12 (6 protons plus 6 neutrons). Thus, hydrogen (1 proton, 0 neutrons) has an atomic weight of 1, oxygen (8 protons, 8 neutrons) an atomic weight of 16. Some familiar elements along with their chemical symbols, atomic numbers, and atomic weights are listed in Appendix A-3.