1. Periodic Table

2. Aufbau Principle
As protons are added one by one to the nucleus to build up the elements, electrons are similarly added to hydrogen like orbitals
The lowest energy level is the 1 s orbital
From this we can begin to diagram the orbitals in an atom +
nucleus
electrons
1 s __
2 s __ p __ __ __
3 s __ p __ __ __ d __ __ __ __ __

3. Aufbau exceptions
You see the first exceptions to the Aufbau principle in the 3d orbital.
Chromium is [Ar]3d54s1
As opposed to the expected [Ar]3d44s2
It then goes back to “normal”, until copper.
Copper is [Ar]3d104s1
There are more examples is the d orbitals below, and in the f orbitals

5. Hund’s Rule
The lowest energy configuration (ground state) for an atom is the one having the maximum number of unpaired electrons allowed by the Pauli Exclusion Principle (two electrons per orbital).
The convention is to represent the spins of electrons as up or down arrows

6. Periodic Table
The modern design of the periodic table is built off of these orbital diagrams

7. You can determine the orbital by the placement
For these elements the last
electrons are filling s orbitals He Li
for these elements
the last electrons are filling
p orbitals
For these elements the last
electrons are filling d orbitals
For the elements the last electrons
are filling f orbitals

9. Electrons configurations are written to shorten orbital diagrams
The electron configuration for potassium is 1s22s2p63s2p64s1
This can be abbreviated to [Ar]4s1
This is the same as saying everything that is in Ar, 1s22s2p63s2p6 +4s1

10. Total order 1 s __ 2 s __ p __ __ __
3 s __ p __ __ __ d __ __ __ __ __
4 s __ p __ __ __ d __ __ __ __ __ f __ __ __ __ __ __ __
5 s __ p __ __ __ d __ __ __ __ __ f __ __ __ __ __ __ __
6 s __ p __ __ __ d __ __ __ __ __
7 s __ p __ __ __ 1 3 2 7 4 5 6 8 13 10 9 11 14 17 12 15 18 16 19

11. Aufbau Principle is the order of filling the orbitals
4s is filled before 3d
The (n+1)s orbitals always fill before the n d orbitals, explained by the penetration effect.
The penetration effect is looking at the forces on the interior electrons in an atom. Not only is there an attraction to the nucleus, but the outer electrons repulsion is pushing these orbitals closer to the nucleus, making them smaller.

12. Ions with Aufbau
Even though 3d is filled after 4s, when an ion is formed it is always the valence electrons that are removed first.
So Fe is [Ar]3d64s2
So Fe2+ is [Ar]3d6
So Fe3+ is [Ar]3d5
Remember, iron always has the nucleus with a large enough effective charge to hold electrons in the d orbital.
It also explains why so many transition metals form +2 ions as one possible stable configuration

13. Lone electron in the 5d or 6 d
Another exception
Lanthanum’s last electron fills the 5d orbital. [Xe]6s25d1
Ce has its last electron fill in the 4f, and the one from 5d (La) jumps to 4f. [Xe]6s24f2
The next elements all fill up the 4f until Gadolinium which fills up the 5d again.
A similar “jumping” of one electron occurs with the actinide series

14. Barium 1 s __ 2 s __ p __ __ __ 3 s __ p __ __ __ d __ __ __ __ __
4 s __ p __ __ __ d __ __ __ __ __ f __ __ __ __ __ __ __
5 s __ p __ __ __ d __ __ __ __ __ f __ __ __ __ __ __ __
6 s __ p __ __ __ d __ __ __ __ __
7 s __ p __ __ __

15. Lanthanum 1 s __ 2 s __ p __ __ __ 3 s __ p __ __ __ d __ __ __ __ __
4 s __ p __ __ __ d __ __ __ __ __ f __ __ __ __ __ __ __
5 s __ p __ __ __ d __ __ __ __ __ f __ __ __ __ __ __ __
6 s __ p __ __ __ d __ __ __ __ __
7 s __ p __ __ __

16. Cerium 1 s __ 2 s __ p __ __ __ 3 s __ p __ __ __ d __ __ __ __ __
4 s __ p __ __ __ d __ __ __ __ __ f __ __ __ __ __ __ __
5 s __ p __ __ __ d __ __ __ __ __ f __ __ __ __ __ __ __
6 s __ p __ __ __ d __ __ __ __ __
7 s __ p __ __ __

17. Praseodymium Nd, Pm, Sm Eu fill the next 4 orbitals in 4 f 1 s __
2 s __ p __ __ __
3 s __ p __ __ __ d __ __ __ __ __
4 s __ p __ __ __ d __ __ __ __ __ f __ __ __ __ __ __ __
5 s __ p __ __ __ d __ __ __ __ __ f __ __ __ __ __ __ __
6 s __ p __ __ __ d __ __ __ __ __
s __ p __ __ __
Nd, Pm, Sm Eu fill the next 4 orbitals in 4 f

18. Gadolinium 1 s __ 2 s __ p __ __ __ 3 s __ p __ __ __ d __ __ __ __ __
4 s __ p __ __ __ d __ __ __ __ __ f __ __ __ __ __ __ __
5 s __ p __ __ __ d __ __ __ __ __ f __ __ __ __ __ __ __
6 s __ p __ __ __ d __ __ __ __ __
7 s __ p __ __ __

19. Terbium 1 s __ 2 s __ p __ __ __ 3 s __ p __ __ __ d __ __ __ __ __
4 s __ p __ __ __ d __ __ __ __ __ f __ __ __ __ __ __ __
5 s __ p __ __ __ d __ __ __ __ __ f __ __ __ __ __ __ __
6 s __ p __ __ __ d __ __ __ __ __
s __ p __ __ __

20. Different Periodic Tables
The electron “jumping” is why there are two forms of the periodic table in common usage.
One has lanthanum and actinium in with the d filling elements.
The other has lanthanum and actinium with the f filling elements

22. To Determine the Condensed electron configuration
Start at the previous noble gas (lower atomic number)
Write out every element in order of atomic number to your given
Determine which shell all elements are filling. The number of elements in that shell is your superscript number.

23. For Iron Previous Noble Gas----Ar Write all elements
K Ca Sc Ti V Cr Mn Fe
These fill 4 s
These fill 3 d
So it is
[Ar]3d64s2

24. Practice
Write out the condensed electron configuration and orbital diagram for…
Nitrogen
Tin
Molybdenum
Rutherfordium

25. Effective Nuclear Charge (Zeff)
Zeff is the net positive charge experienced by a specific electron in a multi electron atom.
As electrons get further away, they will be “shielded” from the nucleus by other electrons.
What is the period trend, with explanation?

27. Ionization Energy The energy required to remove an electron.
What type of ion is produced?
Is the process endothermic or exothermic?
What is the group trend, with explanation?
What is the period trend, with explanation?

29. Exceptions
Normally moving left to right across a period will increase in ionization energy because it is being held in by a stronger nucleus.
However there is an observed dip in ionization energy going from Be to B.
Why?
It is harder to remove an electron from 2p than 3s, these aren’t hydrogen orbitals.
This trend continues for Mg-Al, then you see the trend for Zn-Ga, and Cd-In, and Hg-Tl

30. Another exception
There is another between group 15 and 16 (nitrogen group to oxygen group).
This exception is because in group 15 you have one electron in each of the 3 p orbitals, group 16 has a 4th electron that is easier to remove.

32. Successive Ionization Energies
Ionization energy doesn’t have to stop at one electron, you can remove multiple electrons, to get a 2nd ionization energy I2, 3rd ionization energy I3 …
Why are second ionization energies more than first ionization energies?
Electrons are more easily removed until what occurs?

34. Trends in Ionization Energy
The first ionization energy for phosphorus is 1060 kJ/mol, and that for sulfur is 1005 kJ/mol. Why?

36. Consider atoms with the following electron configurations:
  1s22s22p6
1s22s22p63s1
1s22s22p63s2
 Which atom has the largest first ionization energy, and which one has the smallest second ionization energy? Explain your choices.

37. Atomic Radius ~relative size of an atom.
As you move down a group you are increasing the number of energy levels so the atom is getting larger.
As you move left to right across a period, a more positive nucleus pulls everything in closer, making the atom smaller.
It increases down and to the left.

40. Electron Affinity
Electron affinity is the change in energy when an atom captures a bonding electron.
Energy is normally released, so the number is normally reported as a negative.
What is the group trend, with explanation?
What is the period trend, with explanation?