Science, Tech, Math › Science Periodic Table of the Elements - Accepted Atomic Masses Share Flipboard Email Print Science Chemistry Periodic Table Basics Chemical Laws Molecules 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 05, 2019 The atomic mass (atomic weight) values cited on a periodic table are weighted averages of naturally occurring isotopes. From one year to the next, the values may change slightly (usually only in the last significant digit) as more information about the source of each element becomes available. Periodic Table of the Elements - Accepted Atomic Masses This periodic table contains the atomic masses of the elements as accepted by the IUPAC (09-2013). Todd Helmenstine This black and white periodic table contains the accepted atomic weights of each element as accepted by the IUPAC. This table can be obtained in PDF format here. This table can be used for computer and mobile device wallpapers. The 1920x1080 .png file can be downloaded here (2017 values for all 118 elements). A color version of periodic table with no background or with a black background can be found here. When Not to Use Accepted Values For most chemistry calculations, the most recent table of accepted values should be used. These values do not apply to elements collected anywhere except the Earth's crust. The weighted atomic mass for an element from the Earth's core, the Moon, the Sun, etc., would not be the same as the accepted value. The other time a different value should be used is when dealing with a specific ore sample or other specimen with a known isotope ratio.