Science, Tech, Math › Science How to Define a Pi Bond in Chemistry Share Flipboard Email Print JoJan / Wikimedia Commons / CCA-SA 3.0 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 A pi bond (π bond) is a covalent bond formed between two neighboring atom's unbonded p-orbitals. An unbound p-orbital electron in one atom forms an electron pair with a neighboring atom's unbound, parallel p-orbital electron. This electron pair forms the pi bond. Double and triple bonds between atoms are usually made up of a single sigma bond and one or two pi bonds. Pi bonds are generally denoted by the Greek letter π, in reference to the p orbital. The symmetry of a pi bond is the same as that of the p orbital as viewed down the bond axis. Note d orbitals also form pi bonds. This behavior is the basis of metal-metal multiple bonding.