Science Class 9
Journey Inside the Atom
See what is inside an atom, and how its shells and protons decide the element.
11 lessons · ~74 min total
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Lessons in this topic
- 0 Start here A roadmap: electrons, the nucleus, four atom models, shells, atomic and mass numbers, and outer electrons. · 3 min You are here
- 1 The piece has parts Atoms have smaller parts, and cathode rays showed that electrons are in every atom. · 6 min
- 2 Something with a charge An atom is neutral, so Thomson pictured electrons inside a sphere of positive charge. · 6 min
- 3 Where the mass sits The gold foil experiment showed a tiny, dense nucleus with mostly empty space around it. · 8 min
- 4 A picture that had to change Four models followed one another, and each new result showed what the last one could not explain. · 8 min
- 5 Shells Electrons sit in shells K, L, M and so on, and a shell holds at most 2n² electrons. · 8 min
- 6 Which atom is it The atomic number is the number of protons, and the mass number is protons plus neutrons. · 8 min
- 7 Filling the shells Add one electron at a time and fill K, then L, then M, to get each electronic configuration. · 8 min
- 8 The outer shell decides A full outer shell makes an atom stable, and other atoms lose, gain or share electrons to fill it. · 8 min
- 9 The big picture The whole chapter on one screen. · 4 min
- 10 Track quiz A one-screen cheat sheet, then a question on each idea. · 7 min
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