1. 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.

2. Bohr’s Shell Model + ∆E 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

3. 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
 ↔ 

4. 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

5. 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)
sublevel shape (s,p,d,f) Cl
[Ne] 3s2 3p5
noble gas core

6. + 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 +

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

8. 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)

9. 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

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