Glossary term: Proton
Description: A proton is a subatomic particle with positive electric charge. Protons are one of the main constituents of atomic nuclei, alongside neutrons. The number of protons is the "atomic number" of a nucleus, and each atom with a specific atomic number corresponds to a specific chemical element. The atomic nucleus of hydrogen is a single proton, and the most elementary nuclear fusion reaction in a star is when two protons collide, one of them decays, and a deuteron is formed, consisting of one proton and one neutron. Protons can also be found in the high-energy cosmic rays reaching us from outer space.
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Term and definition status: This term and its definition have been approved by a research astronomer and a teacher
The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".
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Related Diagrams
Nucleon
Caption: A nucleon is a constituent of an atomic nucleus. For normal matter, nucleons can be either protons or neutrons. The number of nucleons defines the mass number of a nucleus while the number of protons defines the atomic number. Atomic nuclei of a particular chemical element all have the same atomic number but can have different mass numbers. Nuclei with the same atomic number but different mass numbers are known as isotopes. Most elements have more than one isotope that occurs in nature although a few only have one isotope that is stable over long periods of time.
This diagram shows the nuclei of isotopes of the first six chemical elements (from left to right: hydrogen, helium, lithium, beryllium, boron and carbon). Beside each chemical element symbol are two numbers. The upper number is the mass number, the number of nucleons. The lower number for each is the atomic number, the number of protons.
Credit: Maria Cristina Fortuna/IAU OAE
License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons
