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Atom video. http://www.youtube.com/watch?v=xqNSQ3OQMGI&feature=share. Basic Principle: electrons occupy lowest energy levels available. Aufbau Principle -- “Bottom Up Rule”. Stern-Gerlach Experiment. . . How could an orbital hold two electrons without electrostatic repulsion?.

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  1. Atom video http://www.youtube.com/watch?v=xqNSQ3OQMGI&feature=share

  2. Basic Principle: electrons occupy lowest energy levels available

  3. Aufbau Principle -- “Bottom Up Rule”

  4. Stern-Gerlach Experiment   How could an orbital hold two electrons without electrostatic repulsion? Electron spin

  5. 2 ways to write electron configurations spdf Notation spdf NOTATION for H, atomic number = 1 1 no. of electrons s 1 sublevel value of energy level Orbital Box Notation ORBITAL BOX NOTATION for He, atomic number = 2 Arrows show electron spin (+½ or -½) 2  1s 1s

  6. Example: Determine the electron configuration and orbital notation for the ground state neon atom. Pauli exclusion principle An orbital can contain a maximum of 2 electrons, and they must have the opposite “spin.”

  7. Write the ground state configuration and the orbital diagram for oxygen in its ground state Hund’s Rule -

  8. Outer electron configuration for the elements

  9. Using the periodic table to know configurations Period 1 2 3 4 5 6 7 Ne Ar Kr Xe

  10. Valence e’s for “main group” elements

  11. Basic Principle: electrons occupy lowest energy levels available Rules for Filling Orbitals Bottom-up (Aufbau’s principle) Fill orbitals singly before doubling up (Hund’s Rule) Paired electrons have opposite spin (Pauli exclusion principle)

  12. Identify examples of the following principles: 1) Aufbau 2) Hund’s rule 3) Pauli exclusion

  13. Shorthand notation practice Examples ●Aluminum: 1s22s22p63s23p1[Ne]3s23p1 ● Calcium: 1s22s22p63s23p64s2 [Ar]4s2 ● Nickel: 1s22s22p63s23p64s23d8 [Ar]4s23d8 {or [Ar]3d84s2} ● Iodine: [Kr]5s24d105p5 {or [Kr]4d105s25p5} ● Astatine (At): [Xe]6s24f145d106p5 {or [Xe]4f145d106s26p5} [Noble Gas Core] + higher energy electrons

  14. Electron configuration for As

  15. Note: Not written according to Aufbau, but grouping according to n

  16. Orbital energy ladder f d n = 4 p d s p n = 3 s p n = 2 s n = 1 Energy s

  17. Phosphorus Symbol:P Atomic Number:15 Full Configuration:1s22s22p63s23p3 Valence Configuration:3s23p3 Shorthand Configuration:[Ne]3s23p3          Box Notation          2s 1s 2p 3s 3p

  18. Quantum numbers and orbital energiesEach electron in an atom has a unique set of quantum numbers to define it{ n, l, ml, ms } • n = principal quantum number • electron’s energy depends principally on this • l = azimuthal quantum number • for orbitals of same n, l distinguishes different shapes (angular momentum) • ml = magnetic quantum number • for orbitals of same n & l, ml distinguishes different orientations in space • ms = spin quantum number • for orbitals of same n,l & ml, ms identifies the two possible spin orientations

  19. Energy levelSublevel# of orbitals/sublevel n = 1 1s (l = 0) 1 (ml has one value) n = 22s (l = 0) 1 (ml has one value) 2p (l = 1) 3 (ml has three values) n = 33s (l = 0) 1 (ml has one value) 3p (l = 1) 3 (ml has three values) 3d (l = 2) 5 (ml has five values) Quantum numbers and orbital energies Each atom’s electron has a unique set of quantum numbers to define it{ n, l, ml, ms } n = principal quantum number (energy) l = azimuthal quantum number (shape) ml = magnetic quantum number (orientation)

  20. Concept: Each electron in an atom has a unique set of quantum numbers to define it{ n, l, ml, ms } 21

  21. Quantum numbers: unique set for each e- • s orbitals p orbitals d orbitals f orbitals • l = 0 l = 1l = 2l = 3 • ml = 0ml = -1, 0, 1ml = -2, -1, 0, 1, 2 ml=-3,-2,-1,0,1,2,3 • An s subshellA p subshellA d subshell An f subshell • One s orbitalThree p orbitalsFive d orbitals Seven f orbitals • For n=1 l=0 an s subshell (with 1 orbital) • For n=2 l=0,1 an s subshell and a p subshell (with 3 orbitals) • For n=3 l=0,1,2 an s subshell, a p subshell, a d subshell (with 5 orbitals) • For n=4 l=0,1,2,3 an s subshell, a p subshell, a d subshell, an f subshell (with 7 orbitals)

  22. Electronic configuration of Br 1s2 2s22p6 3s23p63d10 4s24p5 [Ar]3d104s24p5 [Ar] = “noble gas core” [Ar]3d10 = “pseudo noble gas core” (electrons that tend not to react) Atom’s reactivity is determined by valence electrons valence e’s in Br:4s24p5 highest n electrons

  23. Valence e- shells for transition metalsv.main group elements d orbitals not included in valence shell (pseudo noble gas cores) d orbitals sometimes included in valence shell

  24. Rule-of-thumb for valence electrons Examples ●Sulfur: 1s22s22p63s23p4 or [Ne]3s23p4 valence electrons:3s23p4 ● Strontium: [Kr]5s2 valence electrons:5s2 ● Gallium: [Ar]4s23d104p1 valence electrons:4s24p1 ● Vanadium: [Ar]4s23d3 valence electrons:4s2or3d34s2 Identify all electrons at the highest principal quantum number (n) Use on exams, but recognize limitations Use Table 8.9 for online HW

  25. Selenium’s valence electrons Written for increasing energy: Pseudo noble gas core includes: noble gas electron core d electrons (not very reactive)

  26. Core and valence electrons in Germanium Written for increasing energy: Pseudo noble gas core includes: noble gas core d electrons

  27. d-block: some exceptions to the Aufbau principle Fig. 8.9: Use this table for online homework

  28. Electron spin & magnetism For the ground state oxygen atom: spdf configuration: orbital box notation: Paramagnetic: atoms with unpaired electrons that are weakly attracted to a magnet. Diamagnetic: atoms with paired electrons that are not attracted to a magnet.

  29. Apparatus for measuring magnetic properties

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