1. Electron Configurations

2. Opening Questions

3. Electron Shells and Subshells
We arranged electrons into “shells” labeled n = 1, 2, 3 to indicate the 1st shell, the 2nd shell, etc.
Each “shell” has further divisions called subshells – designated s, p, d, and f.

4. Electron Configurations
Basic idea: electrons occupy lowest energy levels available
n = 1
n = 2 2e
Carbon’s subshells
Where do subshells start?
s: 1st energy level
p: 2nd energy level
d: 3rd energy level
f: 4th energy level

5. Electron Configuration Notation
Electron configuration: a list of all the subshells that have electrons for a given element
Notation: 1
number of electrons in subshell 1 s
subshell
value of energy level

6. Electron Configurations
Which element has the configuration 1s22s22p5?
Period 1 2 3 4 5 6 7 1s 2s 3s 4s 5s 6s 7s 3d 4d 5d 6d 2p 3p 4p 5p 6p 4f 5f
Periodic Table: Subshells
2 elements
10 elements
6 elements
14 elements

7. Electron Configurations
Write the electron configuration for this element.
Period 1 2 3 4 5 6 7 1s 2s 3s 4s 5s 6s 7s 3d 4d 5d 6d 2p 3p 4p 5p 6p 4f 5f
Periodic Table: Subshells
2 elements
10 elements
6 elements
14 elements
How many e- in each subshell?
s: 2 electrons
p: 6 electrons
d: 10 electrons
f: 14 electrons

8. Wrap-up
Identify the element with the following electron configuration.
1s22s22p63s22p64s23d104p3
What is the outermost subshell for bromine, Br?
Name an element with electrons in the f-block.
What is the electron configuration for the element with the atomic number 13?
How many valence electrons does krypton, Kr, have? How do you know?

9. Shorthand Electron Configurations
Instead of writing out all the filled subshells, you can use a shorthand (or noble gas) configuration.
Use the last noble gas as your starting point.
EXAMPLE:
Bromine’s full electron configuration: 1s22s22p63s23p64s23d104p5
Bromine’s shorthand configuration: [Ar]4s23d104p5

10. Shorthand Electron Configurations
Write the shorthand electron configuration for this element
Period 1 2 3 4 5 6 7 1s 2s 3s 4s 5s 6s 7s 3d 4d 5d 6d 2p 3p 4p 5p 6p 4f 5f
Periodic Table: Subshells
2 elements
10 elements
6 elements
14 elements

11. PRACTICE! Go Figure Worksheet…
Start on the backside:
- question #3 b) and d)

12. D-block Elements
Period 1 2 3 4 5 6 7 1s 2s 3s 4s 5s 6s 7s 3d 4d 5d 6d 2p 3p 4p 5p 6p 4f 5f
Periodic Table: Subshells
2 elements
10 elements
6 elements
14 elements
The d-block elements do not follow the nice pattern seen in groups 1, 2,
D-block elements tend to have 2 valence electrons because the s-block before them is full. Those s-block electrons are the valence electrons.
However, it is possible for the first 5 d-block electrons to be valence electrons.