Science, Tech, Math › Science Neutron Definition in Chemistry Composition, Meaning, and Charge Share Flipboard Email Print Talaj / Getty Images Science Chemistry Chemical Laws Basics Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated February 16, 2019 The neutron is the particle in the atomic nucleus with a mass = 1 and charge = 0. Neutrons are found together with protons in the atomic nucleus. The number of neutrons in an atom determines its isotope. Although a neutron has a net neutral electrical charge, it does consist of charged components which cancel each other out with respect to charge. Neutron Facts A neutron is a type of hadron. It consists of one up quark and two down quarks.Although the mass of a proton and a neutron are comparable, especially compared with the much lighter electron, a neutron is slightly more massive than a proton. A neutron has a mass of 1.67492729 x 10-27 kg.A neutron is considered a type of fermion because it has a spin = 1/2.Although it's possible to eject neutrons from the nucleus, the free particles don't last long before reacting with other atoms. On average, a neutron survives on its own about 15 minutes.