1. The Modern Atomic Theory: A Closer Look at the Electron

2. Blocks in The Periodic Table
= s block
= d block
Row #
= p block
= f block 1 2 3 4 5 6 7

3. Where is the Electron?
In the quantum mechanical model, the electrons are found outside the nucleus.
To describe an electron’s location, we can includes
Its Energy Level
Its Sublevel
Its Atomic Orbital

4. Principle Energy Levels
The first horizontal row of the periodic table represents the first or (n=1) principle energy level.
Represented by the letter, n
n = 1  First Energy Level
Each new row on the periodic table starts a new energy level.
Each energy level has a different number of sublevels, a different number of orbitals, and a different number of electrons.

5. The Bohr Model

6. Higher Energy Level = Bigger Sublevel
Sublevels
Based on the number of elements in our Periodic Table, there are four sublevels.
s, p, d, f
Each sublevel has a unique shape.
The size of the sublevel depends on the energy level.
Higher Energy Level = Bigger Sublevel

7. s-Sublevel sphere

8. This is only one of the p-sublevel atomic orbitals.
p-Sublevel dumb bell
This is only one of the p-sublevel atomic orbitals.

9. Since there are 3 orbitals in the p-Sublevel:

10. d-Sublevel
Don’t need to memorize these!

11. f- Sublevel
Don’t need to memorize these!

12. Summary of the Sublevels
Number of Atomic Orbitals
Maximum Number of Electrons s 1 2 p 3 6 d 5 10 f 7 14

13. Atomic Orbitals
All electrons are located in an atomic orbital or orbital.
An atomic orbital represents the area in which there is a 90% chance of finding an electron.
Each atomic orbital can hold two electrons.
Inside these orbitals, electrons take random and unpredictable paths.

14. Processing Your Notes Question #1
1. Which sublevel has a dumbbell shape?
s sublevel
p sublevel
d sublevel
f sublevel
The p-sublevel has a dumbbell shape, while the s-sublevel has a spherical shape.

15. Processing Your Notes Question #2
2. Which sublevels will have the same shape?
3s and 3p
3p and 4p
1s and 2p
4d and 3s
The letter or sublevel determines the shape.

16. Processing Your Notes Question #3
3. Sodium is found on the third row or Period 3 of the periodic table. How many energy levels do the electrons of a sodium atom occupy? 1 3 11 23
3rd Row = 3 Energy Levels

17. Processing Your Notes Question #4
4. How many orbitals are found in a d-sublevel? 4 5 10 14
Be Careful!
The d-sublevel has 5 orbitals and holds 10 electrons.
You will want to memorize that table!

18. Processing Your Notes Question #5
5. How many electrons can be held in one atomic orbital? 2 6 10 14

19. Processing Your Notes Question #6
6. Which letter does not represent a current sublevel of an energy level? d f n p
n represents the energy level not a sublevel.

20. Processing Your Notes Question #7
7. As scientists create new elements, we will need to add new sublevels to the four existing sublevels. In fact, the next sublevel will be called g. After looking at the trend in the number of orbitals for the current sublevels, how many orbitals would you predict would exist in a g-sublevel? 7 8 9 32
s =1
p = 3
d = 5
f = 7
g = 9

21. Putting It All Together1 s 2 2
s & p 4 8 3
s, p, & d 9 18 4
s, p, d, & f 16 32

22. Electron Configurations
Electron Configurations represent the location of the electrons in an atom or ion.
1s22s22p5
the number of electrons
the energy level of the electron (n)
the sublevel

23. Processing Your Notes Question #8
8. How many orbitals are in the fourth energy level? 4 8 16 32
For the fourth energy, you have s, p, d and f.
s = 1 orbital
p = 3 orbitals
d = 5 orbitals
f = 7 orbtials
Add these up!
= 16

24. Processing Your Notes Question #9
9. How many electrons are held in n=2? 2 4 8 16
n=2 means the second energy level.
s = 2 electrons
p = 6 electrons
Add these up!
2 + 6 = 8 electrons

25. Processing Your Notes Question #10
10. Which of the following sublevels does not exist? 1s 2d 3p 4f
On the first energy level, you only have 1s.
On the second energy level, you only have 2s and 2p.
On the third energy level, you only have 3s, 3p, and 3d.
All four sublevels are on the fourth energy level.

26. Processing Your Notes Question #11
11. Which of the following would be an expression used to calculate the number of orbitals based on the energy level (n)? 2n n2
n + 6
2n2
n = 1 n2 = 1
n = 2 n2 = 4
n = 3 n2 = 9
n = 4 n2 = 16

27. Processing Your Notes Question #12
1s22s22p63s23p4
12. Which element is represented by this electron configuration?
sodium
sulfur
argon
selenium
Add up the exponents!
Since it is neutral, protons = electrons.

28. Processing Your Notes Question #13
1s22s22p63s23p4
13. What is the highest energy level in this electron configuration? 2 3 4 6
Energy level represented by the coefficient or the big number.

29. Processing Your Notes Question #14
1s22s22p63s23p4
14. How many electrons are found in the s-sublevel? 2 4 6 8
= 6

30. Processing Your Notes Question #15
1s22s22p63s23p64s23d104p1
15. Which sublevel has the most electrons? s p d f
p = 13 electrons
d = 10 electrons
s = 8 electrons

31. Processing Your Notes Question #16
1s22s22p63s23p64s23d104p1
16. How many electrons are in the highest energy level? 1 2 3 13
The “coefficient” determines the energy, so 4s and 4p are both on the highest energy level.

32. Processing Your Notes Question #17
1s22s22p63s23p64s23d104p1
17. What element is represented by the electron configuration?
titanium
copper
gallium
germanium
Add up the exponents!
Since it is neutral, protons = electrons.

33. Rule #1: Pauli’s Exclusion Principle
Each atomic orbital can hold two electrons.
Sublevel
# of Orbitals
Max # of Electrons s 1 2 p 3 6 d 5 10 f 7 14

34. Rule #2: Aufbau Principle
Electrons will fill the atomic orbital with the lowest energy first.
1s22s22p63s23p64s23d104p5
Lowest Energy  Highest Energy

36. Blocks in The Periodic Table
= s block
= d block
Row #
= p block
= f block 1 2 3 4 5 6 7

38. Sample Electron Configurations
Hydrogen  1s1
Beryllium  1s22s2
Fluorine  1s22s22p5
Chlorine  1s22s22p63s23p5
Potassium  1s22s22p63s23p64s1

39. Important Reminders
Your row number tells you the energy level or coefficient for your configurations.
Know your limits for each sublevel!
You have to use your periodic table be sure that you are following the Aufbau Principle.
1s  2s  2p  3s  3p  3d
1s  2s  2p  3s  3p  4s X

40. Electron Configurations (Containing the d-Sublevel)
The energy level of d-sublevel will ALWAYS be one less than the row or period number.

41. Blocks in The Periodic Table
= s block
= d block
Row #
= p block
= f block 1 2
row # -1 3 4 5 6 7

42. Sample Electron Configurations
Titanium
Iron
Bromine
Tellurium
Silver
1s22s22p63s23p64s23d2
1s22s22p63s23p64s23d6
1s22s22p63s23p64s23d104p5
1s22s22p63s23p64s23d104p65s24d105p4
1s22s22p63s23p64s23d104p65s24d9

43. Where does the f-block “fit in”?
The f-block is considered to be part of periods 6 and 7.

44. Electron Configurations (Containing the f-Sublevel)
The energy level of f-sublevel will ALWAYS be two less than the row number.

45. Blocks in The Periodic Table
= s block
= d block
Row #
= p block
= f block 1 2
row # -1 3 4 5 6 7 6 7
row # -2

46. Sample Electron Configurations
Europium
Tungsten
Bismuth
Bohrium
1s22s22p63s23p64s23d104p65s24d105p66s25d14f6
1s22s22p63s23p64s23d104p65s24d105p66s25d14f145d3
1s22s22p63s23p64s23d104p65s24d105p66s25d14f145d96p3
1s22s22p63s23p64s23d104p65s24d105p66s25d14f145d96p67s26d15f146d4

47. Exceptions to the Rules Make sure you know these!!
Chromium, Cr
Predicted: 1s22s22p63s23p64s23d4
Actual: 1s22s22p63s23p64s13d5
Copper, Cu
Predicted: 1s22s22p63s23p64s23d9
Actual: 1s22s22p63s23p64s13d10

48. Short-Hand Notation [Ne]3s23p2 Noble Gases = He, Ne, Ar, Kr, Xe, Rn
Uses a noble gas (Group 18) to represent the innermost electrons.
Outermost electrons are represented the same way.
Noble Gases = He, Ne, Ar, Kr, Xe, Rn

49. Short Hand Notation Hints
To find the noble gas, look at the noble gas from the previous row or the row above the element.
The energy level or coefficient of the s and p-sublevel is equal to the row or period number.
The energy level or coefficient of
the d-sublevel is one less than the period number and for the f-sublevel two less than the period number.

50. Sample Electron Configurations
Nickel, Ni
Antimony, Sb
Lead, Pb
[Ar]4s23d8
[Kr]5s24d105p3
[Xe]6s25d14f145d96p2
Then combine your d’s!
[Xe]6s24f145d106p2

51. Valence Electrons: Valence Electrons are the electrons in the _______________________ energy level. The energy levels below have the _______________ number of electrons allowed. The number of electrons in the outer level can be found by looking at the highest energy level in the ________________ ____________________ or by looking at the __________________ __________________ located above the column where the element is _________________________. Examples: Mg= Group ___ A so it has _____ valence electrons. Pb= Group ____ A so it has _____ valence electrons.

52. Label the Valence Electrons for each Column on the Periodic Table

53. Draw the Lewis Dot Diagrams for the following elements:
Sodium Magnesium Aluminum
Silicon Phosphorus Sulfur
Chlorine Argon

54. Valence Electrons Electrons in the highest energy level.
1s22s22p63s23p2
What is the highest energy level?
n =3 or third energy level
How many electrons are on the highest energy level?
4 electrons
How many valence electrons are in this element?

55. One Dot for Each Valence Electron
Lewis Dot Diagrams
Element Symbol
One Dot for Each Valence Electron

56. How Are the Dots Arranged?4 8 X 7 1 3 5 6 2

57. He F Ne C Example Dot Diagrams
Write the electron configuration and draw the dot diagrams for each of the following elements.
Helium
Carbon
Fluorine
Neon He F C Ne

58. Short Cut for Valence Electrons13
IIIA 5 B
Boron
Use the group number! 13 Al
Aluminum 31 Ga
Gallium
All of the elements in Group 13 or IIIA will have three valence electrons.

59. Using the Short Cut
Using the short cut, determine the number of valence electrons.
Phosphorus
Argon
Lead
Barium
5 valence electrons
8 valence electrons
4 valence electrons
2 valence electrons

60. Exceptions to the Short Cut
Only works for Group A Elements or the Representative Elements
s and p-blocks ONLY
Helium  two valence electrons

61. Write the electron configuration and draw the Lewis dot diagram for lithium, sodium, and potassium.
The arrangement of electrons helps explains the world around us. In this case, all of the Group 1 elements have similar electron configurations, and therefore, have similar chemical properties.
Alkali Metals in Water

62. Rule #1: Pauli’s Exclusion Principle
Each atomic orbital can hold two electrons with opposite spins.

63. Rule #2: Aufbau Principle
Electrons will fill the atomic orbital with the lowest energy first.
1s22s22p63s23p64s23d104p5
Lowest Energy  Highest Energy

64. Equal energy orbitals are orbitals in the same sublevel.
Rule #3: Hund’s Rule
When filling equal energy orbitals, electrons will arrange themselves to maximize unpaired electrons.
Equal energy orbitals are orbitals in the same sublevel.

65. Orbital Diagrams 3s 2p 1s 2s 1 box = 1 atomic orbital
s-sublevel  1 box
p-sublevel  3 boxes
d-sublevel  5 boxes
f-sublevel  7 boxes
1 arrow = 1 electron