Atomic Structure: Subatomic Particles and Bohr Model

60 lessons, pages 451–510.

  1. Inside the Atom: An Overview — Why atoms are not indivisible after all
  2. Evidence That Atoms Have Parts — Electricity, discharge tubes and charged particles
  3. Cathode Rays — Beams of negative particles in a discharge tube
  4. Thomson Discovers the Electron — Deflection by electric and magnetic fields
  5. The Charge-to-Mass Ratio of the Electron — Why the same particle appears in every element
  6. Millikan and the Charge of the Electron — The oil-drop idea and the elementary charge
  7. The Plum Pudding Model — Thomson's picture of a positive sphere with embedded electrons
  8. Canal Rays and Positive Particles — Goldstein's anode rays and positive ions
  9. Discovery of the Proton — The hydrogen nucleus as a fundamental positive particle
  10. Rutherford's Gold Foil Experiment — Firing alpha particles at a thin metal foil
  11. Interpreting the Gold Foil Results — Why a few alpha particles bounced back
  12. The Nuclear Model of the Atom — A tiny, dense, positive nucleus surrounded by electrons
  13. How Small Is the Nucleus? — Comparing nuclear and atomic diameters
  14. Chadwick Discovers the Neutron — A neutral particle to explain missing mass
  15. The Three Subatomic Particles Compared — Relative charge, relative mass and location
  16. Charges of Subatomic Particles — Relative charges +1, −1 and 0 and the elementary charge
  17. Masses of Subatomic Particles — Why the electron's mass is almost negligible
  18. Why Atoms Are Electrically Neutral — Equal numbers of protons and electrons
  19. What Holds the Nucleus Together? — A first look at the strong nuclear force
  20. Atomic Number — The proton number that defines an element
  21. Atomic Number and the Periodic Table — Moseley and ordering elements by proton number
  22. Mass Number — Counting nucleons: protons plus neutrons
  23. Nuclide Notation — Writing mass number and atomic number with the symbol
  24. Calculating Protons, Neutrons and Electrons — Using atomic number and mass number together
  25. Subatomic Particles in Ions — How gaining or losing electrons changes the count
  26. Mass Number Versus Relative Atomic Mass — Whole-number counts and weighted averages
  27. What Are Isotopes? — Same proton number, different neutron number
  28. Isotopes of Hydrogen — Protium, deuterium and tritium
  29. Isotopes of Carbon — Carbon-12, carbon-13 and carbon-14
  30. Isotopes of Chlorine — Chlorine-35 and chlorine-37 in a 3 : 1 ratio
  31. Chemical Properties of Isotopes — Why electron arrangement makes isotopes react alike
  32. Physical Properties of Isotopes — Differences in mass, density and diffusion rate
  33. Isotopic Abundance — How common each isotope is in nature
  34. Calculating Relative Atomic Mass from Isotopes — Weighted averages from percentage abundances
  35. Finding Abundances from Relative Atomic Mass — Working backwards with two isotopes
  36. The Mass Spectrometer: A First Look — Separating isotopes by mass
  37. Reading a Simple Mass Spectrum — Peaks, mass-to-charge ratios and abundances
  38. Radioactive Isotopes — Unstable nuclei and radiation
  39. Uses of Isotopes — Medicine, dating, tracers and industry
  40. Isotopes, Isobars and Isotones — Classifying nuclides by shared numbers
  41. Problems with Rutherford's Model — Why orbiting electrons should spiral into the nucleus
  42. Light and Line Spectra — Why glowing gases emit only certain colours
  43. Bohr's Model of the Atom — Electrons in fixed energy levels
  44. Energy Levels and Shells — Why shells closer to the nucleus have lower energy
  45. Excitation and Emission — Electrons jumping between shells and releasing light
  46. Flame Tests and Energy Levels — Characteristic colours explained by electron transitions
  47. Shell Capacity and the 2n² Rule — Maximum electrons in each shell
  48. The 2, 8, 8 Filling Pattern — Arranging electrons for the first twenty elements
  49. Writing Electron Arrangements — Notation such as 2,8,1 for sodium
  50. Drawing Bohr Diagrams — Nucleus, shells and electrons on paper
  51. Exploring Atoms in 3D — Building atoms and shells in the ChemVerse simulation
  52. Valence Electrons — The outer shell and its importance
  53. Electron Arrangement and Periodic Table Position — Groups, periods and shells
  54. Noble Gases and Full Outer Shells — Why complete shells mean stability
  55. Electron Arrangements of Ions — Gaining and losing electrons to reach a full shell
  56. Limitations of the Bohr Model — What the model cannot explain
  57. Beyond Bohr: A Preview of Orbitals — From fixed orbits to probability clouds
  58. The Development of Atomic Models — From Dalton to Bohr as a story of evidence
  59. Problem Solving with Atomic Structure — Multi-step questions on particles, isotopes and shells
  60. Atomic Structure: Unit Review — Subatomic particles, isotopes and the Bohr model brought together