Lecture #10
Finishing Chapter 9 now
 CURMUDGEON GENERAL'S WARNING. These "slides" represent highlights from lecture and are neither complete nor meant to replace lecture. It is advised not to use these as a reliable means to replace missed lecture material. Do so at risk to healthy academic performance in 09-105.
Lecture Outline Electron Configurations (continued)

Ionization energies

Second and third ionization energies

Electron Affinity

Valence electrons and electron dot structures in atoms

The energy needed to remove the easiest-to-remove electron from a neutral atom is called the first ionization energy.
First ionization energies for light elements. Using this information, we can estimate the effective nuclear charge, Zeff, for the electron being removed. Helium as an example.
Zeff for lithium
Zeff for neon
The detailed trend in ionization energies for the light elements
The n=1 shell filling
The n=2 shell filling after which the n=3 shell starts
Starting the p-subshell causes a break in the smooth trend across the row.
Starting to pair up electrons after half the p-subshell is filled causes a second break, which we referred to as the mid-shell dip, in the smooth trend across the row.
First ionization energies across rows 1 through 3 of the Periodic Table
Overlapping the 2nd and 3rd row element ionization energies to demonstrate the repeating pattern (determined by valence electron configuration)
Second ionization energies
First, second, and third ionization energies for the light elements
First, second, and third ionization energies shifted to show, again, that valence electron configuration is the determining driver
Electron affinity is the energy involved in adding an electron to a neutral atom to form a negative ion. It is numerically equal to minus the ionization energy for that negative ion. As such, we should expect that the electron affinities also depend on electron configuration.
A pictorial schematic of valence electrons for the Main Group (s- and p-block) elements is shown here where each "dot" represents an accounting of a valence electron. The scheme was invented by G. N. Lewis and these are referred to as Lewis electron dot pictures of elements.
Electronegativity, a property of atoms that will become important in our discussion of molecules.