Outline for Today Friday, Nov. 2 • Chapter 7: Periodic Trends • E ff ective Nuclear Charge • Atomic Size • Ionization Energy • Activation Energy
Effective Nuclear Charge
Why do orbitals with the same principal quantum number, n, increase with angular momentum quantum number, l ? Nucleus (+)
Example Problems: Effective Nuclear Charge • If the core electrons were totally e ff ective at screening the valence electrons and the valence electrons provided no screening for each other, what would be the e ff ective nuclear charge acting on the 5s valence electrons in Strontium ?
Atomic Radius
Trends in Atomic Radius Cs Rb K Na Radius (pm) Li Xe Kr Ar Ne He Atomic Number
Cation and Anion Sizes Li Be B O F Cations are SMALLER than their neutral atoms. Anions are LARGER than their neutral atoms.
Trends in Size in a Group (Column) O Li S Na Se K Te Rb
Example Problems: Atomic Radius • Arrange the following atoms in order of increasing size (smallest to largest) • Ge, K, Kr • Pb, C, Sn, Si • Li, F , Na, H • S 2- ,Ca 2+ , K +
Table 7.2: Ionization Energy
Successive Values of Ionization Energies Increase Element I 1 (kJ/mol) I 2 (kJ/mol) I 3 (kJ/mol) I 4 (kJ/mol) Na 496 4562 Mg 738 1451 7733 Al 578 1817 2745 11577 Si 786 1577 3232 4356
First Ionization Energy
Back to Writing Electron Configurations of Ions! • What is the electron configuration of Ag + ? • How many unpaired electrons does Ag + have?
Some Exceptions to Electron Configuration Rules Electron Electron Element Element Configuration Configuration [Kr] 5s 1 4d 5 Mo Cr [Ar] 4s 1 3d 5 [Kr] 5s 1 4d 7 Ru Cu [Ar] 4s 1 3d 10 Rh [Kr] 5s 1 4d 8 Ag [Kr] 5s 1 4d 10 [Kr] 4d 10 Pd [Xe] 6s 1 4f 14 Au [Xe] 6s 1 4f 14 5d 9 Pt 5d 10
Back to the Challenge Question with Ag + ! • What is the electron configuration of Ag + ? [Kr] 4d 10 How many unpaired electrons does Ag + have? None!
Electron Affinity
Ionization Energy Trends
Ionization Energy for the 2nd Row Elements
Exceptions to Radius Trends
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