1. Advanced Chemistry Unit 6 Quantum Mechanics

2. Advanced Chemistry Unit 6 Quantum Mechanics
Things aren’t always as they seem…

3. Remember,
Protons determine which element it is….
But Electrons determine
what an element will do!
In this unit, we will take a closer look at how electrons behave…..Quantum Mechanics

4. This is the model of the atom developed by Niels Bohr.
It shows the electrons orbiting the nucleus in circular paths
( )

5. In the Bohr model, the valence electrons (the electrons involved in chemical bonding) are shown in the outer ring
Sometimes we use this model to help us imagine how one atom can transfer an electron to another atom
(ionic bonding)

6. In this model, the valence electrons (the electrons involved in chemical bonding) are shown in the outer ring
Sometimes we use this model to help us imagine how one atom can share electrons with another atom
(covalent bonding)

7. A more realistic model of where the electrons are in a Helium atom
Bohr model of a helium atom
The Bohr model works very well for many things, but it really doesn’t show the true complexity of the atom.
In this chapter, we’re going to think about atoms, specifically their electrons, in a more complex way.

8. What do we know about electrons ?
Electrons are moving around the nucleus at very high velocity – not necessarily in circular orbits
Two hydrogen atoms combining to form one H2 molecule
The electrons move so fast that -
it would look like an electron cloud

9. Within the electron cloud, there are areas where you are more likely to find an electron and areas where finding an electron is less likely. Mathematicians call this “probability” An area where you are likely to find electrons is called an orbital.
We will look at the different types of orbitals in a moment. But first, an analogy.

10. The boarding house analogy:
A boarding house has many beds, in various floors and rooms.
Each bed has its own
designation, or address
(the manager’s code)

11. The boarding house analogy – what’s the filling pattern?

12. What is the order in which the beds get filled?
How does the manager keep track of which bed each guest is assigned to?
We can think of electrons
in a similar way.
Electrons will have electron “address” that will tell us where in the atom are located.

13. s orbitals
An s orbital can hold two electrons

14. p orbitals Each p orbital can hold two electrons
There are three variations of bowtie shaped p orbitals
(the difference between them is their orientation in space, like the x, y, and z axes on a graph)

15. d orbitals d orbitals really have interesting shapes……
“double dumbells”
…and a “dumbell
with a donut”!
No, you don’t have to remember these shapes

16. f orbitals
No, you don’t have to remember these shapes either

17. If an atom has several orbitals, you can see how they overlap, making the “electron cloud” have areas where it is more likely to find electrons

18. Ok, this is complicated…
What do I really need to know about electron orbitals?
Orbitals are areas where electrons are likely to be found
Orbitals have different shapes (s=sphere, p=bowtie)
The more electrons an atom has, the more places (orbitals) it will need to hold the electrons
Showing where the electrons are located is like a game, and it is easy if you follow the rules….

19. Electron Orbital Notation
Determine the number of electrons in the atom or ion
Start with the 1s orbital and fill each orbital according to the guide (Aufbau principle)
Show each electron as an arrow
Add arrows (electrons) individually to the boxes until all electrons in the atom have been drawn
Follow Hund’s rule and Pauli’s principle (more on this as we do the practice atoms)

20. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p 3s 2p
Each box can hold 2 electrons

21. Aufbau Principle-
“building up”
an electron occupies the lowest-energy orbital that can receive it
This means start from the 1s and work your way upwards until you use all of electrons

22. Phosphorus
15 electrons
For neutral atoms, the number of electrons is the same as the number of protons
Let’s put them in the proper places on the orbital notation diagram

23. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p
Phosphorus (15 electrons)
The first two electrons go into the 1s orbital
Notice the opposite arrow directions*
13 more electrons to go

24. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p
Phosphorus
The next electrons go into the 2s orbital
11 more to go

25. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p
Phosphorus
The next 6 electrons go into the 2p orbital
One up arrow and one down arrow per box
Fill separately before you double up in the same box
only 5 more to go

26. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p
Phosphorus
The next 2 electrons go into the 3s orbital
only 3 more to go

27. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p
Phosphorus
The last three electrons go into the 3p orbitals.
They each go into separate boxes*
They each show an “up” arrow*

28. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p
Phosphorus
The electron configuration for Phosphorus is
1s22s22p63s23p3

29. Why did we put one arrow up and one arrow down in each box?
Pauli Exclusion Principle- just like no two houses can have the same address, no two electrons in the same atom can have the same “address”. If there are two electrons in the same orbital, we need to make one and the other
(by tradition, we write the up arrow first)

30. When we filled the p orbitals, why did we put one arrow in each box before putting two in the same box?
Hund’s Rule- orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second (fill each energy level separately before you double up)

31. The electron configuration for Phosphorus is
1s22s22p63s23p3

32. electron configuration!

33. Electron Configuration ws
Orbital Diagrams
and
Electron Configuration ws
1-12

34. Manganese
25 electrons
For elements, the number of electrons is the same as the number of protons
Let’s put them in the proper places on the orbital notation diagram

35. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p
Manganese (25 electrons)
The first two electrons go into the 1s orbital
Notice the opposite arrow directions*

36. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p
Manganese
The next electrons go into the 2s orbital

37. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p
Manganese
The next 6 electrons go into the 2p orbital
One up arrow and one down arrow per box

38. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p
Manganese
The next 2 electrons go into the 3s orbital

39. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p
Manganese
The next six electrons go into the 3p orbitals.
That makes 18 electrons done…and 7 more to go

40. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p
Manganese
The next two go into the 4s orbital
20 electrons done…..
5 to go

41. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p
Manganese
The final five electrons go into the 3d level

42. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p
Manganese
The electron configuration for Manganese is
1s2 2s2 2p6 3s2 3p6 4s2 3d5

43. Let’s try some more Li Be B C N O F Ne
This time we’ll save space and show the boxes as lines instead

44. Orbital notation (arrows)
Element
Electron
Configuration
Orbital notation (arrows)
Lithium
(3e-)
1s22s1
____ ____ ____ ____ ____
1s s p
Beryllium
(4e-)
1s22s2
Boron
(5e-)
1s22s2p1
Carbon
(6e-)
1s22s2p2
Nitrogen
(7e-)
1s22s2p3
1s s p
Oxygen
(8e-)
1s22s2p4
Fluorine
(9e-)
1s22s2p5
Neon
(10e-)
1s22s2p6

45. Valence electrons- the electrons involved in chemical bonding…..
…how are these determined?

46. Valence electrons are the electrons in the outermost energy level
These are the electrons that determine if/how an atom will bond with other atoms
1s 2s p s p
Silicon has 4 valence electrons

47. How many valence electrons does Chlorine have?
1s 2s
2p s p

48. Can you locate the valence electrons in this atom of Cobalt ?
Valence electrons are the electrons in the outermost energy level
These are the electrons that determine if/how an atom will bond with other atoms

49. Valence Electrons
How many valence electrons does Bromine have?

50. How many valence electrons does a Bromine ion have?

51. Orbital notation (arrows)
Element
Electron
Configuration
Orbital notation (arrows)
Lithium
(3e-)
1s22s1
____ ____ ____ ____ ____
1s s p
Beryllium
(4e-)
1s22s2
Boron
(5e-)
1s22s2p1
Carbon
(6e-)
1s22s2p2
Nitrogen
(7e-)
1s22s2p3
1s s p
Oxygen
(8e-)
1s22s2p4
Fluorine
(9e-)
1s22s2p5
Neon
(10e-)
1s22s2p6
How many valence electrons does each atom have?

52. Is there an overall pattern?
What are the electron configuration patterns for different families of elements?
Is there an overall pattern?
Chalcogens

53. Electron Configuration for Alkali Metals
Electron configuration end in s1
Outer level has 1 valence electron
1s2 2s2 2p6 3s1
Example: Sodium
1s s p 3s

54. Electron Configuration for Alkaline Earth Metals
Electron configuration ends in s2
2 valence electrons
1s2 2s2 2p6 3s2 3p6 4s2
1s s p 3s
3p 4s

55. Electron Configuration for Halogens
Electron configuration ends in p5
7 valence electrons
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
Example: Bromine
1s s p 3s 3p
1s s p 3s 3p
4s 3d p
4s 3d p

56. Electron Configuration for Noble Gases
Except for Helium, they all end in p6
Helium ends in s2 (it only has 2 electrons)
Atoms are especially stable when the s and p
sublevels are full (8 valence electrons)
Example: Argon
1s s p 3s 3p
1s2 2s2 2p6 3s2 3p6
Outer level (3rd level) has a total of 8 electrons

58. Electron Configuration ws
Orbital Diagrams
and
Electron Configuration ws
13-40

59. Even if you don’t have the electron filling cheat sheet, there are two other ways to figure out the electron configuration:
Create your own cheat sheet
Use the layout of the periodic table

60. Create your own cheat sheet …
(1-7 spdf) 1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f

61. Create your own cheat sheet …
Then fill from the bottom up following the arrows 1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
1s2
= 2 electrons

62. Create your own cheat sheet …
Then fill from the bottom up following the arrows 1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
1s2 2s2
= 4 electrons

63. Create your own cheat sheet …
Then fill from the bottom up following the arrows 1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
1s2 2s2 2p6 3s2
= 12 electrons

64. Create your own cheat sheet …
Then fill from the bottom up following the arrows 1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
1s2 2s2 2p6 3s2 3p6 4s2
= 20 electrons

65. Create your own cheat sheet …
Then fill from the bottom up following the arrows 1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2
= 38 electrons
Notice how the 4th level begins filling before the 3rd is finished filling

66. Create your own cheat sheet …
Then fill from the bottom up following the arrows 1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2
= 56 electrons

67. Use the periodic table layout

68. Use the periodic table layout

69. More Practice:
# e-
Configuration Na 11
1s22s22p63s1 Cl 17
1s22s22p63s23p5 Sb 51
1s22s22p63s23p64s23d104p65s24d105p3 K 19
1s22s22p63s23p64s1

70. Noble Gas “Shortcut” The shape of the periodic table is a helpful clue
When we get to the end of the period, the outermost energy level is full (noble gas)
Write the symbol of the noble gas that comes before the element we are looking for [in brackets]
Then write the rest of the electrons
Magnesium is 1s22s22p63s2
But Neon is 1s22s22p6
Shortcut for Magnesium: [Ne]3s2

71. Noble Gas “Shortcut” Example 3
Write the symbol of the noble gas that comes before the element we are looking for
Then write the rest of the electrons
Chlorine is 1s22s22p63s23p5
Neon is 1s22s22p6
Shortcut for Chlorine: [Ne]3s23p5

72. Noble Gas “Shortcut” Example 4
Write the symbol of the noble gas that comes before the element we are looking for
Then write the rest of the electrons
Potassium is 1s22s22p63s23p64s1
Argon is 1s22s22p63s23p6
Shortcut for Potassium: [Ar]4s1

73. A noble gas cannot be its own shortcut!
Noble Gas “Shortcut”
Example 5
Write the symbol of the noble gas that comes before the element we are looking for
Then write the rest of the electrons
Ex: Argon:
1s22s22p63s23p6
Argon is 1s22s22p63s23p6
Shortcut for Argon: [Ar]
NO!
A noble gas cannot be its own shortcut!

74. Figure out the shortcut for 51Sb
1s22s22p63s23p64s23d104p65s24d105p3
1s22s22p63s23p64s23d104p6 Kr
So, the shortcut is:
[Kr]
5s24d105p3

75. Go backward until you hit a noble gas
Figure out the shortcut for 51Sb using the table Kr
Go backward until you hit a noble gas

76. Figure out the shortcut for 51Sb using the table
5p3
5s2
4d10
[Kr]

77. [Kr] 5s24d105p3 Figure out the shortcut for 51Sb using the table
So, the shortcut for Sb is:
[Kr]
5s24d105p3

78. Write the complete electron configuration and the noble gas shortcut electron configuration for
Polonium (Po)
Xenon (Xe)

79. Electron Configuration ws
Orbital Diagrams
and
Electron Configuration ws