Science, Tech, Math › Science Ground State Definition (Chemistry and Physics) Chemistry Glossary Definition of Ground State Share Flipboard Email Print The ground state is the lowest energy state of an atom or part of an atom. Magictorch/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 July 03, 2019 In chemistry and physics, the ground state is defined as the lowest allowed energy state of an atom, molecule, or ion. In other words, the ground state represents the most stable configuration. If there is more than one possible ground state, degenerate states are said to exist. Even though the species may possess some level of energy, the ground state is considered to have zero-point energy in comparison to other states. If a species has energy greater than the ground state, it is said to be in an excited state. Electrons provide a good example of ground and excited states. If an electron absorbs energy, it may jump to an excited state. At some point, the electron will return to the ground state, typically giving off a photon in the process.