MODELS OF THE ATOMS

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MODELS OF THE ATOMS

  1. 1. Electrons QBA Miguel A. Castro Ramírez
  2. 2. Models of the Atom Red Book: Section 5.1 Blue Book:13.1
  3. 3. Rutherford’s FailureRutherford’s model could not describe behavior of atoms Think About It: Why do certain atoms react while others don’t? Why do some fireworks glow red and others green?
  4. 4. Bohr’s Atom Hypothesis: each electron exists in a certain “orbit” or “energy level” Electrons can never exist in between Higher energy levels are further from the nucleus
  5. 5. QuantaA quantum (pl. quanta) is the amount of energy required for an electron to move up an energy level
  6. 6. Quantum Mechanical ModelAlso called “electron cloud model”Mathematically-based
  7. 7. Quantum Mechanical Model Determines allowed electron energies and how likely it is to find an electron in various locations around the nucleus Dense cloud = high probability
  8. 8. Atomic Orbitals Region of space in which there is a high probability of finding an electronWhy It’s Important: The exact location of each electroncontrols the atom’s properties!
  9. 9. “Address” of ElectronEach electron will be found  On a PRINCIPAL ENERGY LEVEL  In one of several SUBLEVELS  On an ORBITAL
  10. 10. Principal Quantum Numbers Each energy level is assigned a principal quantum energy number, n n can be 1, 2, 3, or 4, etc…
  11. 11. Sublevels Each principal energy level has specific sublevels where an electron can be found # of sublevels corresponds to principal quantum number  Level 1 has 1 sublevel  Level 2 has 2 sublevels…
  12. 12. SublevelsSublevels are given letter designationsspdf
  13. 13. The orbital names (s,Why s, p, p, d, f, g, h,...) ared, and f? derived from the characteristics of their spectroscopic lines: sharp, principal, diffuse and fundamental, the rest being named in alphabetical order. For mnemonic reasons, some call them spherical & peripheral.
  14. 14. Atomic Orbitalss sublevel – 1 orbitalsp sublevel – 3d sublevel – 5f sublevel – 7
  15. 15. Atomic Orbitals Each orbital can hold one pair of electrons Each member of the pair has an opposite spin
  16. 16. How many totalelectrons in each?
  17. 17. 1 Principal Energy Level st• 1 sublevel (s)• 2 electrons in s orbital• 2 total
  18. 18. 2 Principal Energy Level nd• 2 sublevels (s and p)• 2 electrons in s orbital• 6 electrons in p orbitals• 8 total (10 combined with 1st)
  19. 19. 3 Principal Energy Level rd• 3 sublevels (s, p and d)• 2 electrons in s orbital• 6 electrons in p orbitals• 10 electrons in d orbitals• 18 total (28 combined with 1st and 2nd)
  20. 20. 4 Principal Energy Level th• 4 sublevels (s, p, d and f)• 2 electrons in s orbital• 6 electrons in p orbitals• 10 electrons in d orbitals• 14 electrons in f orbitals• 32 total (50 combined with 1st, 2nd, and 3rd)
  21. 21. Electron Arrangement Blue Book: 13.2 Red Book: 5.2
  22. 22. Electron ConfigurationWay that electrons are arranged in various orbitalsArrangement governed by three rules
  23. 23. Aufbau PrincipleElectrons first occupy orbitals of lowest energySublevels from some principal energy levels overlap others
  24. 24. Aufbau Diagrams Display the order in which orbitals are filled (to achieve the most stable configuration)
  25. 25. Aufbau Principle
  26. 26. Pauli Exclusion PrincipleEach orbital holds, at most, two electrons.Two occupy the same orbital, two electrons must have opposite spins.This is written or
  27. 27. Hund’s Rule In each sublevel, one electron enters each orbital until each has one with the same spin direction Not until all orbitals have one electron can any have two
  28. 28. Orbital Filling DiagramsShow which orbitals are filled by electrons
  29. 29. Writing Electron Configurations
  30. 30. Electron Configurations Sublevels are filled in the following order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s
  31. 31. Electron ConfigurationsContain 3 items: Number represents energy level Letter represents sublevel Superscript represents number of electrons 1s 2
  32. 32. Electron ConfigurationsAdditional segments needed for each sublevel 1s 2s 2 2
  33. 33. Electron Configurations1s 2s 2p2 2 6
  34. 34. Electron Configurationsof Specific ElementsIn a neutral element, the number of electrons is equal to the number of protons.
  35. 35. Electron ConfigurationsHydrogen SiliconOxygen CalciumNeon Superscripts add up to the total number of electrons!

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