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/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 9.7 Isotopes https://www.khanacademy.org/science/chemistry/atomic-structure-and-properties/introduction-to-the-atom/v/atomic-weight-calculation 2026-03-26T05:40:45.96433927Z Worked example: Atomic weight calculation How to calculate atomic weight from atomic mass and percent abundance of carbon isotopes. Sal Khan video https://cdn.kastatic.org/googleusercontent/BCIZ-co8ICgwinRbkBTQFBDQDjUqWP6E1yvR2g5VxJ-rkwxYBluTnvu3JxSv-WfCF5iS4ML_cQmSOv3qI9Od7TEi Worked example: Atomic weight calculation How to calculate atomic weight from atomic mass and percent abundance of carbon isotopes. https://cdn.kastatic.org/ka-youtube-converted/EPvd-3712U8.mp4/EPvd-3712U8.mp4 267 9.7 Isotopes https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:atomic-structure-and-properties/x2eef969c74e0d802:mass-spectrometry-of-elements/v/isotopes 2022-09-07T08:21:01.673602243Z Isotopes Isotopes are atoms of the same element with different numbers of neutrons. Because they contain different numbers of neutrons, isotopes have different atomic masses. The average atomic mass of an element is calculated by taking the weighted average mass of the element's naturally occurring isotopes. Sal Khan video https://cdn.kastatic.org/ka_thumbnails_cache/0a383f46-3f5b-4b2c-ad63-6338ab2a71be_1280_720_base.png Isotopes Isotopes are atoms of the same element with different numbers of neutrons. Because they contain different numbers of neutrons, isotopes have different atomic masses. The average atomic mass of an element is calculated by taking the weighted average mass of the element's naturally occurring isotopes. https://cdn.kastatic.org/ka-youtube-converted/ShC3VoxxW3g.mp4/ShC3VoxxW3g.mp4 328 9.7 Isotopes https://www.khanacademy.org/science/class-9-chemistry/x46dd29ce84a663ea:structure-of-the-atom/x46dd29ce84a663ea:atomic-number-mass-number-isotopes-and-isobars/v/worked-example-identifying-isotopes-and-ions 2021-03-18T10:33:23Z Worked example: Identifying isotopes and ions Identifying isotopes and ions from the number of electrons, protons and neutrons, and vice versa.  video https://cdn.kastatic.org/googleusercontent/lifCymNe8jSpWZ8PDns689V6TAPEOUKLR6BZvEYueut1r3KwY4GrgT9UmX5v5LOUff8kLwadt3nDhbugyVQHBGw Worked example: Identifying isotopes and ions Identifying isotopes and ions from the number of electrons, protons and neutrons, and vice versa.  https://cdn.kastatic.org/ka-youtube-converted/koAFBScR41A.mp4/koAFBScR41A.mp4 225 9.7 Isotopes https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:atoms-isotopes-and-ions/x2613d8165d88df5e:isotopes-and-ions/e/apply-isotopes 2024-01-03T14:35:52.595781343Z Apply: isotopes Apply your understanding of isotopes in this set of free practice questions. Lauren Rosebrugh exercise