Science, Tech, Math › Science Angular Momentum Quantum Number Definition Share Flipboard Email Print The angular momentum quantum number determines the shape of an electron orbital. p orbitals are the result of an angular momentum quantum number equal to 1. Adisonpk / 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 12, 2019 The angular momentum quantum number, ℓ, is the quantum number associated with the angular momentum of an atomic electron. The angular momentum quantum number determines the shape of the electron's orbital. Also Known As: azimuthal quantum number, second quantum number Example: A p orbital is associated with an angular momentum quantum number equal to 1. History The angular momentum quantum number came from the Bohr model of the atom, as proposed by Arnold Sommerfeld. The lowest quantum number from spectroscopic analysis had an angular momentum quantum number of zero. The orbit was considered to be an oscillating charge, which appeared as a sphere in three dimensions. Source Eisberg, Robert (1974). Quantum Physics of Atoms, Molecules, Solids, Nuclei and Particles. New York: John Wiley & Sons Inc. pp. 114–117. ISBN 978-0-471-23464-7.