1. EMR and the atom: Part Deux
EMR and the atom: Part Deux
on to electron configurations from wave information

2. What you’ve seen so far….
Model of a Nitrogen (z=7) atom

3. Which is really not true- why?
Because orbitals- the “electron cloud” are
3-D, not flat
are not round in most cases
e-s are spread out as much as possible
(e-s are moving very rapidly)

4. Sublevels and Orbitals
The electrons are spread out in orbitals that have varying
Shapes
Energy (distance from nucleus)
The orbitals are described in regards to their quantum numbers
Descriptions that are descriptive and hierarchical
There are 4 numbers that describe an orbital
Written as follows: (#, #, #, ±#)

5. Principal quantum number (n)
Describe the
distance from the nucleus of the orbital
The energy of the orbital
Values for n are integers
The smallest possible value is 1
As the distance from the nucleus (and therefore energy) increases, the number increases

6. Quantum numbers

7. There periodic table and n
The 7 periods on the periodic table correspond to n values
Each period has a unique n value
For the 1st period, n=1
For the 2nd period, n=2
And so on….

10. Angular Momentum (l) (this is a script l, as in llama)
Angular Momentum (l) (this is a script l, as in llama)
Is the shape of the sublevel
s =0
p =1
d =2
f = 3

11. The s sublevel

12. p sublevel

13. d sublevel

14. Another look at d sublevel

15. f sublevel

16. General tutorials for electron configuration stuff
some slides in this PowerPoint are from this site already
See key equations and concepts (select from menu on the left), as well as the looking through the overview where to the tutorials are listed (links for just those are on the left, too)

18. Magnetic number (ml) Denote the orbital sublevel that is filled
Denote the orbital sublevel that is filled
s sublevesl have one orbital; a sphere has one orientation in space
p sublevels have three orbitals; 3 orientations in space
d sublevels have five orbitals; 5 orientations in space
f sublevels have seven orbitals; 7 orientations in space

19. “Flavors” of orbitals
s sublevels have one orbital; a sphere has one orientation in space

20. “Flavors” of orbitals
p sublevels have three orbitals; 3 orientations in space

21. “Flavors” of orbitals
d sublevels have five orbitals; 5 orientations in space

22. “Flavors” of orbitals
f sublevels have seven orbitals; 7 orientations in space

23. Spin
Spin is +½ or -½
Up or down (could say clock wise and counter-clock wise)

24. How we use this….
There is a specific order to how the e- fill the orbitals; it is not random
Although there are exceptions to the rules (last thing we do)

26. The principles of e- configuration
The Aufbau (next) Principle:
That e- fill the lowest energy sublevel before going to the next sublevel
The Pauli Exclusion Principle:
That e-s are paired according to opposite spins
Hund’s Rule:
e-s spread out in equal energy orbitals before pairing electrons

27. The first level to fill is the 1s level
It is the lowest energy sublevel
It holds two electrons
They are oppositely paired (up and down- ↑↓)
Each sublevel (each __) holds 2 electrons

29. Next… The second sublevel is the 2s sublevel
It also holds 2 electrons (because s holds 2, not because of the number),
also oppositely paired ↑↓

31. 1s2, 2s2,then comes 2p6 So, as it states above
1s fills, 2s fills ,then comes 2p
It holds up to six electrons
Because p orbitals hold 6 electrons

32. Next… From 2p, Notice, you follow the arrows
From 2p,
3s fills with 2e-, then onto
3p, with 6e- then
4s with 2e- followed by
3d with 10e- (because d holds 10e-)
Then 4p with 6e-
Notice, you follow the arrows
Remember, the number of electrons comes from the letter (the orbital’s momentum, m)

33. The sublevels of the orbitals are first filled, then you continue onto the next level (Aufbau)
Also be sure to place one electron in each sublevel prior to filling the level (↑ ↑ ↑ and not ↑↓ ↑ _) (Hund)
e-s must be paired with e-s of opposite spin (↑↓, not ↑↑ or ↓↓) (Pauli)

34. Putting it all together…
Carbon (neutral, so 6 electrons)
What this would look like:
↑↓ ↑↓ ↑ ↑ _
1s 2s 2p
(notice there are 6 arrows for 6 electrons)
This can also be written as 1s2 2s2 2p2
Notice the superscripts add up to 6

36. There are some exceptions…
This is because some energy levels are very close together
electrons are able to move between close orbitals in order to minimize repulsion
Example: the 4s and 3d orbitals are very close in energy
So exceptions for some period 4 d block elements occur
Cr is not 1s2 2s2 2p6 3s2 3p6 4s2 3d4
Cr is 1s2 2s2 2p6 3s2 3p6 4s1 3d5
Because it takes less energy to split the electrons between the 5 sublevels than it does to put them together in the 4s and 3d