Science, Tech, Math › Science Why Do Protons and Neutrons Stick Together? How the Strong Force Works in an Atomic Nucleus Share Flipboard Email Print Altayb / Getty Images Science Chemistry Molecules Basics Chemical Laws 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 November 06, 2019 An atom contains protons, neutrons, and electrons. The nucleus of an atom consists of bound protons and neutrons (nucleons). The negatively charged electrons are attracted to the positively charged protons and fall around the nucleus, much like a satellite is attracted to the gravity of the Earth. The positively-charged protons repel each other and aren't electrically attracted or repelled to the neutral neutrons, so you may wonder how the atomic nucleus sticks together and why protons don't fly off. The explanation for why protons and neutrons stick together is known as "the strong force." The strong force is also known as the strong interaction, color force, or strong nuclear force. The strong force is much more powerful than the electrical repulsion between protons, however, the particles have to be close to each other for it to stick them together. How the Strong Force Works Protons and neutrons are made up of smaller subatomic particles. When protons or neutrons get close enough to each other, they exchange particles (mesons), binding them together. Once they are bound, it takes considerable energy to break them apart. To add protons or neutrons, the nucleons either have to be moving at high speed or they need to be forced together under great pressure. Although the strong force overcomes electrostatic repulsion, protons do repel each other. For this reason, it's usually easier to add neutrons to an atom than to add protons.