1. Electron Configuration

2. Remember
Electrons do not travel around the nucleus of an atom in orbits

3. Remember
They are found in energy levels at different distances away from the nucleus.

4. Remember
Only a certain number of electrons may exist in an energy level, but the number varies. It can be determined by:
energy level 1 = 2
energy level 2 = 8
energy level 3 = 18
energy level 4 = 32

5. Levels and Sub Levels Electrons cannot exist between energy levels
(like the rungs of a ladder).
Energy levels are broken up into sublevels:
There are at least 4 possible types of sublevels—given labels: s, p, d, or f

6. Sub Groups We will not be concerned about what they look like.
We will be responsible for understanding where electrons are within the sub groups
There are four subgroups: s p d f

8. s Orbital
Full name: Sharp
Maximum Electrons: 2
Shells: All

9. p Orbital Full name: Principal Maximum Electrons: 6
Shells: 2nd & Higher

10. d Orbital Full name: Diffuse Maximum Electrons: 10
Shells: 3rd & Higher

11. f Orbital Full name: Fundamental Maximum Electrons: 14
Shells: 4th & Higher

12. Electron Energy Level Notes
An easy way to remember this is to use the periodic table--it is arranged to show how these orbitals are filled.

13. Rules to Follow Pauli Exclusion Principle
Maximum of 2 electrons are found in the same orbital
(“orbital” means a particular location)
Each one has an opposite “spin”, allowing them to take up the same space.

14. Rules to Follow
The aufbau principle states that each electron occupies the lowest energy orbital available.
Ex: 4s is never filled before 2p.

15. Let’s Work Backwards The electron configuration for Oxygen, O:
1s2 2s2 2p4
Find Oxygen on the periodic table:

16. De-code the code The electron configuration for Oxygen, O: 1s2 2s2 2p4
Now let’s analyze the code:

17. De-code the code The electron configuration for Oxygen, O: 1s2 2s2 2p4
We can identify that Oxygen is the 4th element in the 2p subgroup.
Therefore the “4” that is in the code must refer to its placement within the sub group.

18. De-code the code The electron configuration for Oxygen, O: 1s2 2s2 2p4
If this is the ending point, then we fill in the subgroups before.
1s & 2s
(Remembering that s subgroup can only have 2 electrons)

19. De-code the code The electron configuration for Oxygen, O: 1s2 2s2 2p4
Consider the atomic structure of oxygen:

20. De-code the code The electron configuration for Oxygen, O: 1s2 2s2 2p4
The exponent refers to the number of
electrons present in the subgroup.
The coefficient must refer to the
shell level of each subgroup.

21. De-code the code The electron configuration for Oxygen, O: 1s2 2s2 2p4
Identify that adding all exponents=
number of electrons for the element.
Thus, adding up electrons for each
coefficient would identify the number
of electrons on each shell.
Ex: 2+4=6 (# of e- on 2nd shell)

22. Valence Electrons
Elements in the same group have the same number of valence electrons in their outermost shell.
Elements having same number of valence electrons in their atoms possess similar chemical properties.

23. Order of the code

24. Order of the code

25. Order of the code

26. Order of the code

27. Order of the code