Todays goals

1
Todays goals

• Order of electron removal
• Zeff and periodic trends

2
Admin stuff

• New OWLs More will be posted after class
• Reading current Ch. 8
• Test 2 Mon, Oct 23th, 600-730 PM
• Extra SI study session 6-8 PM Sunday in library
  (1320)
• Next week Tuesday SI study session cancelled
• Wednesday SI study session will review exam
• Office hours this week (I will be in either my
  office or the CRC)
• Fri from 230-430 PM

3
What is the electron configuration of Ti?

• 1s2 2s2 3s2 4s2 2p6 3p6 3d2
• 1s2 2s2 3s2 4s2 2p6 3p6 4d2
• 1s2 2s2 3s2 2p6 3p6 3d4
• 1s2 2s2 3s2 2p6 3p6 4d4
• 1s2 2s2 2p6 3s2 3p6 3d4
• 1s2 2s2 2p6 3s2 3p6 4d4
• 1s2 2s2 2p6 3s2 3p6 4s2 3d2
• 1s2 2s2 2p6 3s2 3p6 4s2 4d2

4
Transition metals / box diagrams
Hunds rule electrons prefer to be unpaired with
the same spin.
You should be able to write out the configuration
for the first 40 elements (through Zr) with the
use of the periodic table.
5
Which are the most stable configurations?

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

• Note that sometimes the filling order of
  electrons is changed because of the extra
  stability of half-full orbitals (example Cr, Cu)
• Think of this as a stability bonus (extra credit)
  for the entire atom outweighing the penalty for
  one electron not being in the lowest energy
  orbital available

6
Removal order (a) maximum n (b) maximum l
(if same n)
Filling order (a) minimum nl (b) minimum n
(for same nl)
Electrons removed in same order as added except
4s electrons are removed before 3d electrons
6s and 5d electrons are removed before 4f
electronsSimilar behavior in higher periods (ie
5s before 4d)
Why are the patterns different?
7
The relative energies of the orbitals subshells
are different for neutral atoms and ions.
Ions have more or fewer electrons than neutral
atoms.
Ti2 has more or fewer electrons than neutral
Ti? A more B fewer
What is the configuration of Ti2? Mn2? As2?
8
Effective nuclear charge

• Each electron feels a combination of attractive
  forces from the nucleus and repulsive forces from
  other electrons in the atom
• Can approximate the interplay between these
  forces by assigning an effective nuclear charge,
  Z, which is lower than the nuclear charge, Z.

9
Z simulation

• http//www.cowtownproductions.com/vining/Sims/effe
  ctive_nuclear_charge_s.html
• core electrons vs. valence electrons

• Core electrons shield strongly (S 0.7 / e)
• Valence electrons shield weakly (S 0.3 / e)
• We are most often concerned with energy of the
  valence electrons

10
Effective nuclear charge (Z) vs l
This is why different subshells with same n have
different E!