https://www.khanacademy.org/science/biology/history-of-life-on-earth/radiometric-dating/a/atomic-number-atomic-mass-and-isotopes-article 2021-04-29T07:51:16Z Atomic number, atomic mass, and isotopes Fundamental properties of atoms including atomic number and atomic mass. The atomic number is the number of protons in an atom, and isotopes have the same atomic number but differ in the number of neutrons. article https://www.khanacademy.org/science/class-9-chemistry/x46dd29ce84a663ea:atoms-and-molecules/x46dd29ce84a663ea:what-is-an-atom/v/atomic-mass-2 2021-05-25T21:59:59Z Atomic mass Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. video https://cdn.kastatic.org/googleusercontent/5YusxUCLO6XEhz_eswj4WT-vKQncR_cKC41-TLReVPtw8G0u9t0sILZGODGLR_7DPWL70bk1HPlZDeiupbzr00Xp Atomic mass Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. https://cdn.kastatic.org/ka-youtube-converted/b0sYucYw6F0.mp4/b0sYucYw6F0.mp4 513 Atomic mass https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:atoms-isotopes-and-ions/x2613d8165d88df5e:isotopes-and-ions/v/average-atomic-mass 2022-07-29T13:48:23.370439724Z Average atomic mass The average atomic mass (sometimes called atomic weight) of an element is the weighted average mass of the atoms in a naturally occurring sample of the element. Average masses are generally expressed in unified atomic mass units (u), where 1 u is equal to exactly one-twelfth the mass of a neutral atom of carbon-12. Sal Khan video https://cdn.kastatic.org/googleusercontent/1rWF_Sm-ov4z3_Tm3RojlNxBlONAGoAJE-b9W7zP9blvbt1VpVl3g7vXDYrT6ccW1nQG9pZLgV6kp-R-tibaw5XudchkKh6hQZ6y Average atomic mass The average atomic mass (sometimes called atomic weight) of an element is the weighted average mass of the atoms in a naturally occurring sample of the element. Average masses are generally expressed in unified atomic mass units (u), where 1 u is equal to exactly one-twelfth the mass of a neutral atom of carbon-12. https://cdn.kastatic.org/ka-youtube-converted/YsqoF3hqdkg.mp4/YsqoF3hqdkg.mp4 518 Atomic mass https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:atoms-isotopes-and-ions/x2613d8165d88df5e:isotopes-and-ions/e/apply-calculating-average-atomic-mass 2026-03-06T03:50:42.250138425Z Apply: calculating average atomic mass Apply your understanding of average atomic mass in this set of free practice questions. Allen Ruch exercise