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Modern Atomic Model

Modern Atomic Model

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Modern Atomic Model

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  1. Modern Atomic Model

  2. Periodic Law • When elements are arranged in order of increasing atomic number, the elements with similar properties occur at periodic (regular) intervals. • The periodic table is a graphical representation of the periodic law.

  3. Periodic Table Periods are the rows across – look at your gold periodic table – there are 7 periods Groups or Families are the columns – look at your gold periodic table – there are 2 sets of numbers above the columns – some regular and some Roman numerals. We will use the regular numbers so there are Groups 1 – 18.

  4. Electron orbits • Neils Bohr had electrons in energy levels. His planetary model had electrons in orbits.

  5. Electron orbits • Orbits are predictable paths. • Great for planets but it doesn’t work for electrons.

  6. Electron orbits • Can’t know with any certainty where an electron is or where it will be an instant later. • Can’t plot the path of an electron. • Electrons are not in orbits!

  7. We need a new model!Atomic Orbitals • The modern quantum mechanical model has electrons in energy levels that have sublevels with orbitals. orbital - region around nucleus where an electron of particular energy is likely to be. Orbital for a hydrogen atom Think of the places where you would find a firefly in the dark.

  8. It’s not really that hard. • Get out your laminated gold periodic table. • Refer to it as we go through a whole bunch of mind-boggling slides!!!!!

  9. We are going to look at the atomic numberson the table as electron numbers—each electron added to an atom occupies a space on the table.

  10. s-block p-block d-block f-block

  11. Let’s look at the periodic table as a “block diagram” Each block is a sublevel within an energy level s p d f

  12. Sublevels have orbitals • Each orbital can hold a maximum of 2 electrons

  13. s-block p-block d-block f-block

  14. Go across any row in an s sublevel– how many numbers (electrons) across? At 2 electrons/orbital how many orbitals in an s sublevel?

  15. Go across any row in a p sublevel– how many numbers (electrons) across? At 2 electrons/orbitalhow many orbitals in a p sublevel?

  16. Go across any row in a d sublevel– how many numbers (electrons) across? At 2 electrons/orbitalhow many orbitals in a d sublevel?

  17. Go across any row in an f sublevel– how many numbers (electrons) across? At 2 electrons/orbitalhow many orbitals in an f sublevel?

  18. Energy Levels Have Sublevels s sublevel 1 orbital p sublevel 3 orbitals 5 orbitals d sublevel

  19. Number of Orbitals /Sublevel 1 for an s sublevel, 3 for a p sublevel, 5 for a d sublevel and 7 for an f sublevel. • The maximum number of electrons in an orbital does not vary. It is 2.

  20. Atomic Orbitals

  21. Arrangement of Sublevels in Energy Levels • Energy level 1 has 1 sublevel 1s • Energy level 2 has 2 sublevels 2s, 2p • Energy level 3 has 3 sublevels 3s, 3p, 3d • Energy level 4 has 4 sublevels 4s, 4p, 4d, 4f Number of sublevels = Energy Level

  22. s sublevel has 1 orbital s orbital: lowest energy holds 1 pair of electrons 1s 2s 3s 1s

  23. p sublevel has 3 orbitals p orbitals: hold 3 pairs of electrons p x

  24. d sublevel has 5 orbitals d orbitals: holds 5 pairs of electrons

  25. f sublevel has 7 orbitals f orbitals: hold 7 pairs of electrons Orbital Gallery

  26. 1st Energy Level s Electrons will fill in the sublevel with the lowest energy state first before filling in the next sublevel. s 2nd Energy Level p s Increasing Energy 3rd Energy Level p It so happens that the 4s sublevel is at a lower energy state than the 3d sublevel. d Increasing Distance from Nucleus s p 4th Energy Level d Electrons will fill in the 4s sublevel before they go back and fill the 3d sublevel. s f p 5th Energy Level d f

  27. s-block p-block d-block f-block

  28. 1s 1s 1 2 2s 2p 3 3p 3s 4 4p 4s 3d 5p 4d 5 5s 6 6s 5d 6p 7s 6d 7 4f 5f

  29. Block Diagram s p 1 2 3 4 5 6 7 d (n-1) 6 7 f (n-2) © 1998 by Harcourt Brace & Company

  30. Getting Started: • Each box represents an orbital • Orbitals are in groups according to sublevels • Arrows represent electrons • Any single orbital can hold a maximum of 2 electrons

  31. A. General Rules • Each orbital can hold TWO electrons with opposite spins.

  32. A. General Rules • Electrons fill the lowest energy orbitals first. • “Lazy Tenant Rule”

  33. A. General Rules • Within a sublevel, place one e- per orbital before pairing them. • “I don’t want to share my room if I don’t have to!” RIGHT WRONG

  34. Block Diagram s p 1 2 3 4 5 6 7 d (n-1) 6 7 f (n-2) © 1998 by Harcourt Brace & Company

  35. 2s 2p 1s B. Notation • Orbital Diagram O 8e-

  36. Homework Read pages 135 – 138 Do Orbital Diagrams Worksheet – both sides.