1. Orbitals What you need to know: Some things to keep in mind:
What order to fill the orbitals as you get more electrons
Even easier than figuring the number of electrons per energy level
We’ll do that after going over the shapes and locations of the orbitals
- Octet Rule
Some things to keep in mind:
You don’t have to know the shapes, so don’t freak out about them
You don’t really need to know this for most things you would do as a chemist, though it will help.
Something neat to be familiar with as it helps to visualize what we mean when we talk about valence electrons in a later chapter. It also helps make sense as to what it means by having 4 orbitals in energy level 2.
Observe that they are trying to get as close to the positively charged nucleus as possible (opposite charges attract) while at the same time are trying to avoid each other as much as possible (similar charges repel).
What we will be doing today.

2. (& Similar charges repel)
Orbitals
Electrostatic Force – the force that keeps electrons attracted to the nucleus – the opposite charges attract each other
Electrons have a negative charge
Protons have a positive charge
OPPOSITES ATTRACT
(& Similar charges repel)

3. Orbitals
This is basically a packing problem … electrons want to get as close as possible to the nucleus (opposites charges attract each other) while staying as far away from each other as possible (similar charges repel each other). At some point, the repulsion of the similar charges of electrons won’t allow any more in the space of that orbital
Very, very simplistic explanation

4. 1st Energy Level
Energy level 1 has:
1 orbital
Maximum of 2 electrons

5. Orbitals 1s Energy level 1 has one orbital The 1s orbital
1 stands for energy level
S stands for the shape
1s1 means there’s 1 electron
1s2 means there are electrons
Is a sphere – can visualize as a ball.

6. 2nd Energy Level Energy level 2 has: 4 orbitals Maximum of 8 electrons
One s orbital
Three p orbitals
Maximum of 8 electrons

7. Orbitals 2s One orbital is the 2s orbital Energy level is 2
S stands for the shape
Again spherical, but now a little bigger and enclosing the S1
He in this picture means the 1s orbital that we find in He
Like a ball within a ball.

8. Orbitals 2p Energy level 2 has 4 orbitals The 2S orbital (one)
The 2p orbitals (three) (jacks)
Are 3 p orbitals
p orbitals are oriente on the x, y, z axes (length, width, height)
<<< hmmm … they overlap with the S orbitals but still extend beyond them … thus available to interact with other electrons!
Like a jack in the game Jacks – where you have a ball and jacks. First, note that this configuration allows the electrons to be as far apart from each other while they are as close the nucleus as possible. The second BIG thing is, note that just the tips of the p orbitals stick out of the s orbital. This means there are up to (but no more than) 8 electrons on the “outside” of the electron cloud / atom.

9. 3rd Energy Level Energy level 3 has: 9 orbitals
One s orbital
Three p orbitals
Five d orbitals
Maximum of 18 electrons

10. Orbitals 3s One 3s orbital
An even bigger S orbital enclosing the 1s, 2s, 2p orbitals

11. Orbitals 3p Energy level 3 has three p orbitals
The 3S orbital (one orbital)
The 3p orbitals (three orbitals)
Notice again, the p orbitals have just the tips outside the s orbital, allowing for up to, but no more than 8 electrons on the “surface” of the atom.

12. Orbitals 3d Energy level 3 has five d orbitals
The 3s orbital (one orbital, 2 electrons)
The 3p orbitals (three orbitals, 6 electrons)
The 3d orbitals (five orbitals, 10 electrons)
These are interspersed around the p orbitals
So, I don’t have a drawing of these orbitals in relation to the others, but please note the IMPORTANT fact that they are all within the s orbital. Thus even though there are even more electrons than before, there are still only up to 8 electrons on the “surface” of the atom. This will be VERY important to us soon!

13. Electron Configuration
Another way of showing where the electrons are located.
Ex: Helium = 1s2
1 = energy level
S = type of orbital
2 = number of electrons
Ex: Lithium = 1s22s1
1 & 2 = energy levels
2 & 1 = number of electrons

14. Orbital Energy Levels Orbitals can have different energy levels too
Note that the 4s orbital is a lower energy level than the 3d. Since electrons want to fill the lowest energy orbital they can first, the 4s will be filled before the 3d.
Thanks to our hero Aufbau, knowing which orbitals to fill first is easy to remember!
Orbitals have different energy levels WITHIN the energy level they occupy. Electrons ALWAYS fill the lowest energy levels first! (This is called the Aufbau Rule. Aufbau is the German word for “order”, or the order that orbitals are filled in.) Just like water always fills the bottom of a glass first, never from the top down. Therefore, since the 4s orbital is lower than the 3d orbitals, it will be filled first even though it is technically in a higher energy level. All this means is that it takes less energy to fill the 4s orbital than trying to stuff even more electrons within the 3rd energy level. Think of it like packing for a trip – at some point it becomes easier to just pack a second suitcase than try and stuff all your clothes into the one.

15. Aufbau Chart
Energy Level
Nucleus
Energy level 1 has 1 type of orbital (s)
Energy level 2 has 2 types of orbitals (s & p)
Energy level 3 has 3 types of orbitals (s & p & d)
The Aufbau (“order”) chart. This is an easy way to remember which orbitals are filled in first. Note on each energy level that the order of orbitals is spdf. Note too, that each energy level has as many orbitals as the energy level, up to a max of “f”. (While theoretically it can be more, there are no atoms large enough for a “g” orbital, so up through “f” is all the further you need to go.) Also note that the chart is NOT read left to right, but at a diagonal. When you reach the end of the orbitals in the diagonal, you go to the next diagonal arrow and follow it. This is a much easier way than memorizing the order to fill orbitals! Everyone needs to be able to read it & Pre-AP needs to be able to draw this chart. Note that it only goes to 7p. This accounts for all 7 energy levels we have discovered to date. It also corresponds to the 7 rows of the periodic table!
Just remember – if you forget this, it’s a speedy F (spdf).

16. Electron Configurations
The maximimum number of electrons for each orbital are:
s = 2
p = 6
d = 10
f = 14
note that each orbital holds 4 more than the previous!
Just listing the electrons in order of how they are filled for each atom / element
Just follow the aufbau chart along the diagonal lines

17. Electron Configurations
The electron configuration for H is:
1s1
or, the electron is in the 1st energy level, s-orbital, and there is 1 electron
For Lithium, it is: 1s2 2s1
or, the electrons are located (in order filled) in the 1st energy level, s-orbital, and there are 2 of electrons, and the 2nd energy level, in the s-orbital, has 1 electron.
Just follow the aufbau chart along the diagonal lines

18. Orbitals through 4s

19. All the shapes of the orbitals

20. Group Work
Aufbau Chart (just do one) & electron configurations for H through Ne

21. Exit Ticket
Aufbau Chart (just do one) & electron configurations for Li and C

22. Bell Work
Day 2 Electron Config

23. Group Work 1
Day 2 Electron Config

24. Exit Ticket & HW
Day 2 Electron Config

25. Quiz

26. Valence Electrons
The outer shell of electrons are called the valence electrons
These are important because it’s the outer electrons that interact with each other (form bonds between atoms)
There will never be more than 8 valence electrons
Because we fill the d orbital is “buried” under the s & p orbitals, these (s & p orbitals) are always on the outer shell (2 + 6 = 8)

27. Electron Dot Structures
As Chemists we are primarily concerned with the valence electrons
Electron Dot Structures give us an easy, quick way of visualizing the valence electrons
For now just need to know the electron dot structures for H through Ne

28. Dot Structure for Hydrogen

29. Dot Structure for Helium

30. Dot Structure for Lithium

31. Dot Structure for Beryllium

32. Dot Structure for Oxygen

33. Dot Structure for Fluorine

34. Calculating Average Atomic Mass
Convert the percentages into decimals. (This percentage is known as its relative abundance or percent abundance)
Multiply the percentage of each isotope by its respective mass.
Add the numbers from step two together.

35. Calculating Average Atomic Mass
Example:
Isotopes At. Mass Abundance 24Mg % 25Mg % 26Mg %
( x ) + ( x ) + ( x ) = =

36. Group Work

37. Octet Rule (An introduction)
Octet Rule: The outer shell of an atom always wants to be full (or in the case of H empty).
The prefix octo- means 8
Atoms want to be neutral, but also want their outer shell of electrons to be full
They want to be like the Noble Gases

38. Octet Rule The S orbital (2 electrons) is the outer layer for H & He
H only has 1 valence electron
He only has 2 valence electrons

39. Octet Rule The p orbital can hold 6 electrons
With the s orbital’s 2 electrons this equals 8
These 8 electrons (or lack thereof) primarily determine the interactions of all the elements

40. Octet Rule 8 is the “magic” number!
So … except for the first period of elements (H & He) …
8 is the “magic” number!

41. Octet Rule
The first shell (energy level) only needs 2 electrons to be full
After that, all the shells need 8 electrons to be full
Therefore:
If there are less than 4 electrons, the atoms will want to give them away to other elements
If there are more than 4 electrons, the atoms will want to take them from other elements

42. Octet Rule Just remember:
The number of electrons to fill the first shell is 2
The number of electrons to fill all the other shells is 8

43. Octet Rule If you forget, Look at the period (row) the element is in
That will tell you the number of shells
Look at the group / family (column) the element is in
That will tell you the number of valence electrons

44. Worksheets
Draw Bohr models for K - Kr

45. The End

46. Spherical Radii of the Orbitals

47. Aufbau Chart
Chemistry Physics
Energy Level Energy Level
Nucleus
A Chemist views energy levels based on how they are filled in real life, as well as how they will interact with other atoms. An energy level is filled when the outer electrons (valence electrons) equal 2 (as in He), or 8 (as in Ne & Ar). This is much more practical and a better predictor of how the atoms will interact with each other.
2 e-
8 e-
18 e- 1 2 3 4
The easiest way to remember the number of electrons to fill an energy level in Chemistry is to count the number of boxes in a period (horizontal line) on the periodic table.

48. Group Work
Can we make the Principles come out?
Table