1. Electron Configuration
Where do the electrons really hang out??
In those crazy orbitals!!
EC = The arrangement of electrons around a nucleus.

2. Let’s use the orbital shapes to place electrons.
Helium 2 Oxygen

3. Not sure about you…
I think that is a royal pain!

4. There is an easier way- Electron Configuration!
There are seven energy levels (we only worry about the first 4).
Within the levels are subshells (s, p, d, f)
Each subshell can accommodate a certain number of orbitals
Each orbital can contain 2 electrons

5. Electron Configuration
3 Rules:
Aufbau Principle
Pauli Exclusion Principle
Hund’s Rule

6. Aufbau Principle Electrons enter the lowest energy level first
Different levels within a principal energy level can overlap the energy levels of an adjacent principal level
The filling of atomic orbitals does not follow a simple pattern.

7. Aufbau Principle- Here’s the pattern!!
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f

8. Pauli Exclusion Principle
An atomic orbital may
describe at most 2 electrons
1 or 2 electrons may occupy
an orbital
When an orbital contains
2 electrons, they must have
an opposite paired spin

9. Pauli Exclusion Principle
Because of their magnetic moments, we generally represent electrons using a single barbed arrow. The tip of the arrow points to the magnetic north of the electron

11. Hund’s Rule
When electrons occupy orbitals of equal energy (s, p, d, f), one electron enters each suborbital until all orbitals contain 1 electron with the same parallel spin
The second electrons then add to each orbital so that their spins are paired.
Filling seats on a school bus

12. Heisenberg Uncertainty Principle
“The more precisely the position is determined, the less precisely the momentum is known in this instant, and vice versa.”
It is impossible to know the velocity and position of the electron at the same time.

13. Lets do the EC for using the rules! (Show MO and EC)
Fluorine Sodium

14. Do electron configuration practice worksheet

15. Some things to note
Valence electrons are those in the outer s and p orbitals. Shared and unpaired electrons can be determined by looking at the outermost, incomplete orbital.

16. We can just use Aufbau– it is a little easier
1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f
Oxygen Silicon Calcium

17. Use Aufbau to determine these EC’s
1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f
Li Phosphorus Vanadium

18. Now try worksheet 2

19. Work on your Valence electron WS for 10 minutes!
Compare answers, discuss what you may be doing wrong. Questions for me?

20. Can we tell which element by looking at the EC?
Warm Up
Can we tell which element by looking at the EC?
1s22s22p63s23p5
1s22s22p63s23p64s2 3d10
You can project this while you are taking roll… answers are on the next slide

21. How did you do Count the number of electrons
1s22s22p63s23p5 = 17 electrons, Chlorine
1s22s22p63s23p64s2 3d10= 30 electrons, Zinc

22. Did you write this in your notes?
Valence electrons are those in the outer s and p orbitals. Shared and unpaired electrons can be determined by looking at the outermost, incomplete orbital.

23. Noble Gas Configuration…
Write the noble gas in the period above the element… add the rest of the electron configuration.
Example:
Long form for Phosphorus: 1s22s22p63s23p3
Noble Gas Configuration for Phosphorus
Nobel gas above P = Ne
[Ne] 3s23p3

24. Now you try!
Write the noble gas configuration for V (atomic #23) La (atomic #57) Lr (atomic #103)

25. We can also use the periodic table to determine EC.
Try the periodic table method…

26. You need to be careful which periodic table you use for this
You need to be careful which periodic table you use for this!! The Web-Elements PT works well…

27. Ground, Excited or Impossible?
Ground- If the electrons are in the orbitals that you would expect them to be in. Excited- If some of the electrons are in a higher energy level. Impossible- If the orbital doesn’t exist and/or the EC doesn’t make any sense.

28. What happens with Ions??
Ions gain or lose electrons… What is the electron configuration for the magnesium cation? What about S2-

29. When removing electrons …
Remove the last electrons that were placed… Unless there are electrons in the d orbital…then remove the last s electrons first.

30. Isoelectronic…
Different atoms that have the same electron configuration. Na1+ Ne F1-

31. Identify the atoms
An element that has a 2- charge that is isoelectronic with Neon.

32. Identify the atoms
An atom that has lost 3 electrons and is isoelectronic with He

33. Identify the atoms
An element that has a 2- charge that is isoelectronic with Neon. An atom that has lost 3 electrons and is isoelectronic with He An atom that has gained one electron and has the same EC as Cu.