SUMMARY Unit 01 (Chp 6,7): Atoms and Periodic Properties Chemistry, The Central Science, 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten SUMMARY Unit 01 (Chp 6,7): Atoms and Periodic Properties John D. Bookstaver St. Charles Community College St. Peters, MO  2006, Prentice Hall, Inc.

Bohr’s Shell Model + ∆E EXCITED state (1913–Niels Bohr) EXCITED state e–’s emit (–) energy, move back to inner levels (n=5 to n=2) e–’s absorb (+) energy, move to outer levels (n=2 to n=5) + GROUNDstate 5 4 3 2 ∆E 2 2 Which transition shows a light wave of the greatest energy? n=5 to n=2

Photon (Light) Calculations Given wavelength () of light, one can calculate the energy (E) of 1 photon of that light: Speed of light: Plank’s constant: 2.998  108 m/s 6.626  10–34 J•s (constants) c =  (given on Exam) E = h  ,  (inverse) E ,  (direct) Avogadro’s number: 6.022  1023 particles 1 mole  ↔ E  ↔ 

Where are the electrons really? (Shell) principle energy level (n) (1,2,3,4 …) (Sub-shell) shape (Orbital) 3-D arranged (Electron) spin up/down (not rings) s (1) p (3) d (5) f (7) x y z

Electron Configuration (arrangement) Orbital Notation +8 # of e–’s in each orbital Oxygen (O) 1s2 2s2 2p4 1s2 2s2 2p4 6 Na 1s2 2s2 2p6 3s1 How many valence e–’s? (outer level) Al 1s2 2s2 2p6 3s2 3p1 energy level (shell, n) orbital shape (s,p,d,f) Cl [Ne] 3s2 3p5 noble gas core

+ 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p2 nucleus Aufbau: Fill lowest energy orbitals first. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p2 Hund’s: 1 e– in equal orbitals before pairing () (3d fills after 4s) ? Pauli Exclusion: -Where should we start placing electrons first? -Opposite spin alleviates repulsion. -All single before double. no e–’s same props (opp. spin) (↑↓) nucleus +

Photoelectron Spectroscopy (PES) Which peak is H and which is He? higher peak = more e–’s 1s2 Relative # of e–’s He 1s1 H 6 5 4 3 2 1 0 Binding Energy ...or Ionization Energy (required to remove e–’s) (MJ/mol)  further left = more energy required (stronger attraction due to more protons)

Periodic Trends We will explain observed trends in Zeff & shielding Atomic (and Ionic) Radius Ionization energy Electronegativity size lose e– attract e– Zeff & shielding (explains ALL periodic trends and properties)

Zeff & Shielding attraction shielding Zeff Na atom effective nuclear charge, (Zeff): Zeff = Z − S Z = nuclear charge (+proton’s) S = shielding (core e–’s) attraction shielding Zeff shielding, (S): inner core e–’s shield valence e–’s from nuclear attraction. Z = +11 +11 Zeff = +1 Na atom

Periodic Trends (Summary) Electronegativity Can you explain all of this in terms of p’s and e’s? Zeff & shielding Electronegativity Atomic radius