Todays goals

1
Todays goals

• Magnetism
• Ionic size
• Ionization energy
• Electron affinity

2
Admin stuff

• OWLs
• Test 2 Oct 23rd, 600-730 PM, 65 Bartlett
• Chapters 78 only
• Review session Monday during class
• SI Review Sunday, 6-8 PM, Library room 1320
• Office hours today 230 430 PM (office or
  CRC)

3
Bulk vs atomic magnets

• Diamagnet all e are paired (no free spins)
• Paramagnet unpaired e (spins align w/field)
• Ferromagnet paramagnetic material where spins
  align with each other

Paramagnet
Ferromagnet

• We can use electron configurations to predict the
  magnetism of atoms, but not molecules or extended
  solids.

4

• Nitrogen gas (N2) is observed to be a
• A diamagnet
• B paramagnet
• C ferromagnet

5
Core vs. valence

• Valence electrons
• Main group s and p electrons in outermost shell
• Transition metals outermost s and d electrons
• Core electrons
• Innermost electrons, chemically inert
• Which are the valence electrons in
• Mg Ne 3s2
• Fe Ar 4s2 3d6
• Ge Ar 4s2 3d10 4p2

6
Shielding (S) and Effective nuclear charge (Z)

• S Z Z (always)
• Approximate rules for determining shielding
• Core electrons fully shield valence electrons
• 1s electrons fully shield 3s electrons (S 1)
• Valence electons partially shield valence
  electrons
• 2p electrons partially shield 2p electrons (S
  0.35)
• 2s electrons partially shield 2p electrons (S
  0.35)
• Outer electrons do not shield inner electrons
• 2s electrons do not shield 1s electrons (S 0)

7
Shielding (S) and Effective nuclear charge (Z)

• Core electrons fully shield valence electrons
• 1s electrons fully shield 3s electrons (S 1)
• Valence electrons partially shield valence
  electrons
• 2p electrons partially shield 2p electrons (S
  0.35)
• 2s electrons partially shield 2p electrons (S
  0.35)

• F 1s22s22p5 S 2x1 6x0.35 Z 9-S 4.9
• Ne 1s22s22p5 S 2x1 7x0.35 Z 10-S 5.55
• Na 1s2 2s2 2p6 3s1 S 10x1 Z 11-S 1

(4.10)
(4.45)
(10.00)
8
Covalent (neutral) radii of the elements
Largest elements have the smallest effective
nuclear charge for their relative of electrons
Smallest elements have the largest effective
nuclear charge for their relative of electrons
For the same Z, large n orbitals are bigger than
small n orbitals
9
Ionization energies (Ch. 8-6)

• Ionization energy is the energy needed to remove
  an electron from an atom.

• Ionization energies are obtained in the gas phase
  by spectroscopic techniques.
• A(g) -gt A(g) e-

DE ionization energy

• Compounds with low ionization energies can easily
  become positive ions (cations)

10
First ionization energies
Configuration of B, B Configuration of O, O
Periodic trends (1) Hardest to ionize elements
on right (2) Hardest to ionize elements on top
11
Which are the most stable configurations?

• Completely full s, p, d, and f orbitals
• Half full s, p, d, and f orbitals