https://www.khanacademy.org/science/chemistry/atomic-structure-and-properties/history-of-atomic-structure/v/rutherfords-gold-foil-experiment 2022-09-27T05:27:31.474935863Z Rutherford’s gold foil experiment Learn about Rutherford's discovery of the nucleus and the development of the nuclear model of the atom. video https://cdn.kastatic.org/googleusercontent/GUca1q02zeVjSuVtBIXH6p52GSGoDXIJ1yEl6cYQ4J1y8JlCk2lZbfkLapmLiIsRJkG0n-vitdeSdc31H9toW26p Rutherford’s gold foil experiment Learn about Rutherford's discovery of the nucleus and the development of the nuclear model of the atom. https://cdn.kastatic.org/ka-youtube-converted/bVlwH1kfDeg.mp4/bVlwH1kfDeg.mp4 684 What is inside atom? https://www.khanacademy.org/science/class-9-chemistry/x46dd29ce84a663ea:structure-of-the-atom/x46dd29ce84a663ea:models-of-an-atom/v/drawback-of-the-rutherford-model 2023-06-26T12:36:08.867767149Z Drawback of the Rutherford model What are the drawbacks of the Rutherford model? Let's find out! Vibhor Pandey video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Drawback of the Rutherford model What are the drawbacks of the Rutherford model? Let's find out! https://cdn.kastatic.org/ka-youtube-converted/NdjUIozumbE.mp4/NdjUIozumbE.mp4 223 What is inside atom? https://www.khanacademy.org/science/class-9-chemistry/x46dd29ce84a663ea:structure-of-the-atom/x46dd29ce84a663ea:models-of-an-atom/v/bohr-s-model-of-an-atom 2023-06-26T12:36:08.867767149Z Bohr's model of an atom How did Bohr respond to the drawbacks in the Rutherford model? Let's find out! Vibhor Pandey video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Bohr's model of an atom How did Bohr respond to the drawbacks in the Rutherford model? Let's find out! https://cdn.kastatic.org/ka-youtube-converted/haFTkhOcQaY.mp4/haFTkhOcQaY.mp4 130 What is inside atom? https://www.khanacademy.org/science/class-9-chemistry/x46dd29ce84a663ea:structure-of-the-atom/x46dd29ce84a663ea:models-of-an-atom/e/atomic-structure 2026-04-03T18:30:01.793877038Z Atomic structure Test your knowledge of atomic structure! Ashley exercise https://www.khanacademy.org/science/class-9-chemistry/x46dd29ce84a663ea:structure-of-the-atom/x46dd29ce84a663ea:how-are-electrons-distributed-in-various-shells/v/electron-distribution-in-shells 2023-06-26T12:36:08.867767149Z Electron distribution in shells How are electrons distributed in the shells around the nucleus? Do they follows any rules? Let's find out! Vibhor Pandey video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Electron distribution in shells How are electrons distributed in the shells around the nucleus? Do they follows any rules? Let's find out! https://cdn.kastatic.org/ka-youtube-converted/H4bvY_CkSf0.mp4/H4bvY_CkSf0.mp4 605 What is inside atom? https://www.khanacademy.org/science/class-9-chemistry/x46dd29ce84a663ea:structure-of-the-atom/x46dd29ce84a663ea:how-are-electrons-distributed-in-various-shells/e/electron-distribution-in-an-atom-and-calculation-of-valency 2026-04-07T09:22:30.618598699Z Electron distribution in an atom/ion and calculation of valency. Let's solve a few problems to calculate valency and see how electrons are distrubuted in an atom. Aanchal Arora exercise https://www.khanacademy.org/science/class-9-chemistry/x46dd29ce84a663ea:structure-of-the-atom/x46dd29ce84a663ea:atomic-number-mass-number-isotopes-and-isobars/v/isobars 2023-06-26T12:36:08.867767149Z Isobars We've seen atoms of same elements with same atomic number but different atomic masses, but now, let's have a look at atoms of different elements with same atomic mass! Vibhor Pandey video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Isobars We've seen atoms of same elements with same atomic number but different atomic masses, but now, let's have a look at atoms of different elements with same atomic mass! https://cdn.kastatic.org/ka-youtube-converted/9xwmJ_aI-6o.mp4/9xwmJ_aI-6o.mp4 149 What is inside atom? 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 What is inside atom? 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 What is inside atom? 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 What is inside atom? https://www.khanacademy.org/science/class-9-chemistry/x46dd29ce84a663ea:structure-of-the-atom/x46dd29ce84a663ea:atomic-number-mass-number-isotopes-and-isobars/e/isotopes-and-isobars 2026-04-08T08:09:55.69362548Z Isotopes and Isobars Let's solve a few problems to understand the concept of isotopes and isobars. Aanchal Arora exercise