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ATOMIC ELECTRON CONFIGURATIONS AND PERIODICITY

Learn about the arrangement of electrons in atoms, quantum numbers, electron filling order, HUND’S RULE, and the configurations of different elements. Discover the importance of electron configurations in understanding the periodic table.

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ATOMIC ELECTRON CONFIGURATIONS AND PERIODICITY

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  1. ATOMIC ELECTRON CONFIGURATIONS AND PERIODICITY

  2. Arrangement of Electrons in Atoms Electrons in atoms are arranged as SHELLS (n) SUBSHELLS (l) ORBITALS (ml)

  3. QUANTUM NUMBERS n ---> shell 1, 2, 3, 4, ... l ---> subshell 0, 1, 2, ... n - 1 ml ---> orbital -l ... 0 ... +l ms ---> electron spin +1/2 and -1/2

  4. Pauli Exclusion Principle No two electrons in the same atom can have the same set of 4 quantum numbers. That is, each electron has a unique address.

  5. See “Toolbox” for Electron Configuration tool.

  6. Electron Filling OrderFigure 8.5

  7. spdf notation for H, atomic number = 1 1 no. of s 1 electrons value of l value of n Writing Atomic Electron Configurations Two ways to write configs. One is called spdf notation.

  8. Writing Atomic Electron Configurations Other is called the orbital box notation. One electron has n = 1, l = 0, ml = 0, ms = + 1/2 Other electron has n = 1, l = 0, ml = 0, ms = - 1/2

  9. Lithium Group 1A Atomic number = 3 1s22s1 3 total electrons

  10. Beryllium Group 2A Atomic number = 4 1s22s2 ---> 4 total electrons

  11. Boron Group 3A Atomic number = 5 1s2 2s2 2p1 ---> 5 total electrons

  12. Carbon: Group 4A Atomic number = 6 1s2 2s2 2p2 ---> 6 total electrons Here we see for the first time HUND’S RULE. Electrons in orbitals having the same energy are placed singlyas long as possible.

  13. Nitrogen Group 5A Atomic number = 7 1s2 2s2 2p3 ---> 7 total electrons HUND’S RULE. When placing electrons in the same energy, we place them singly as long as possible.

  14. Oxygen Group 6A Atomic number = 8 1s2 2s2 2p4 ---> 8 total electrons HUND’S RULE. When placing electrons in the same energy, place them singlyas long as possible.

  15. Fluorine Group 7A Atomic number = 9 1s2 2s2 2p5 ---> 9 total electrons

  16. Neon Group 8A Atomic number = 10 1s2 2s2 2p6 ---> 10 total electrons Note that we have reached the end of the 2nd period, and the 2nd shell is full!

  17. Sodium Group 1A Atomic number = 11 1s2 2s2 2p6 3s1 or “neon core” + 3s1 [Ne] 3s1 (uses rare gas notation) All Group 1A elements have [core]ns1 configurations.

  18. Calcium Group 2A Atomic number = 20 1s2 2s2 2p6 3s2 3p6 4s2 [Ar] 4s2 All Group 2A elements have [core]ns2 configurations n is the period number.

  19. Aluminum Group 3A Atomic number = 13 1s2 2s2 2p6 3s2 3p1 [Ne] 3s2 3p1 Group 3A elements [core] ns2 np1 n is the period number.

  20. Phosphorus Group 5A Atomic number = 15 1s2 2s2 2p6 3s2 3p3 [Ne] 3s2 3p3 All Group 5A elements have [core ] ns2 np3 configurations where n is the period number.

  21. Transition MetalsTable 8.4 All 4th period elements have the configuration [argon] nsx (n - 1)dy and so are “d-block” elements. Chromium Iron Copper

  22. Lanthanides and Actinides All these elements are “f-block” elements. Cerium [Xe] 6s2 5d1 4f1 Uranium [Rn] 7s2 6d1 5f3

  23. Electron Configurations and the Periodic Table

  24. “Your Best Friend” • Periodic table

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