Electron Configurations

1
Electron Configurations

• Fully filled shells are lower in energy then
  partially filled shells
• ie. Noble gases are most stable
• For partially filled shells
• fully filled subshells are lower in energy than
  partially filled subshells
• ½ filled subshells are lower in energy than
  partially filled subshells
• Cu exception Ar 4s13d10 rather than Ar
  4s23d9
• Cr exception Ar4s13d5 rather than Ar4s23d4

2
Atomic Radius

• Larger principle quantum larger shells (down
  columns)
• Zeff Z S
• Z of protons
• S Screening effect (e- in lower energy
  shellscore)
• Within a shell, Zeff increases across the row.
  Therefore, radius decreases.

3
Bonding Atomic Radius

• Bonding Radii are slightly smaller than
  nonbonding radii
• Bond distance is predicted by sum of bonding
  radii for each atom

4
Ion Radii

• Cations (pink) are smaller than the atom (gray)
  which are smaller than the anion (blue)
• More positive charge smaller
• More negative charge larger

5
Ionization Energy (I)
Energy required to remove an electron from a
gaseous atom or ion
X (g) ? X (g) e-
DHI is postive

• Larger I, harder to remove e-
• I1 lt I2 lt I3 ect.
• See table 7.2
• Noble gases highest
• Metals are lower
• Irregularities due to partially vs. half filled
  shells

6
Electron Affinity
X (g) e- ? X- (g)
DHEA is negative
Energy change associated with the addition of an
electron to a gaseous atom

• EA increases (more negative) across a periodic
  row
• Eeff increases across a row
• F releases the most energy (notice irregularities
  due to half/full shells)
• EA has irregular trend down a periodic group
• A lower electron-nucleus attraction is
  counterbalanced by a lower electron-electron
  repulsions

7
Electron Configuration of Ions
Note underlined electrons are valence electrons

• F (9 electrons)
• 1s22s22p5
• F- (10 electrons)
• 1s22s22p6 (Full valence shell)
• Na (11 electrons)
• 1s22s22p63s1
• Na (10 electrons)
• 1s22s22p6 (empty valence shell)