1. Electron Configuration
Ch 13

2. Review 7 energy levels electrons can be found in
As the number of electrons increases, you fill more energy levels
Each energy level contains certain sublevels that hold a specific number of electrons
s (holds 2 electrons), p (6), d (10), f(14)

3. Electron Configuration
Arrangement of electrons in the energy levels and sublevels
Always fill the lowest energy sublevel first
Use Aufbau principle to correctly fill the energy levels and sublevels in order

4. Electron Configuration for Sodium
How many electrons does Sodium (Na) have? 11
What is the first sublevel electrons fill? 1s
How many electrons can fit in the 1s sublevel? 2
What is the second sublevel electrons fill? 2s
How many electrons can fit in the 2s sublevel?

5. What is filled after the 2s sublevel? 2p
How many electrons can fit in the 2p sublevel? 6
How many electrons are left that need a sublevel?
2+2+6=10 have been used
1 left over
What sublevel does the one electron belong to? 3s

6. How to write Electron Configurations
Write the sublevels in order from least energy to most energy
Write the total number of electrons in each sublevel as a superscript off the sublevel
Example: Sodium (Na)
1s22s22p63s1

7. Iron (Fe) How many electrons does Fe have?26
What is the electron configuration for Fe?
1s22s22p63s23p64s23d6
*Remember the 3d sublevel has more energy than the 4s energy level so you fill the 4s sublevel first.

8. What element has the electron configuration 1s22s22p63s23p64s23d104p3?
If you count the electrons, you can then use that to determine the atomic number and name of the element.
Since there are 33 electrons, the element is As

9. Periodic Table and Electron Configurations
periodic table shows periodicity,
elements in the same group have similar properties
Holds true for electron configurations
The last sublevel you fill relates to what group you are in
If last sublevel to fill is the s sublevel
Element is in groups 1 or 2
p sublevel
groups 13-18
d sublevel
groups 3-12
f sublevel
Element is a lanthanoid or actinoid

10. Kernel Structure Short hand way to show electron configuration
To write a kernel structure
Need to know the noble gas that comes before the element you are writing the kernel structure for
Example:
What is the noble gas that comes before Beryllium (Be)?
Helium (He)

11. Write the symbol of the noble gas within brackets
Then follow with the rest of the elements electron configuration
Whenever you are writing kernel structures
Noble gas is always followed by a s sublevel
The period of the element that follows your noble gas will tell you the energy level you are in

12. Beryllium (Be)
Kernel structure
[He]2s1
Long hand version:
1s22s1

13. What is the kernel structure for Selenium (Se)?
First, what is the noble gas the period above selenium?
Argon
What period is Selenium in?
4th
Kernel structure for selenium is:
[Ar]4s23d104p4

14. What are the only 2 elements that do not have kernel structures?
H and He
Because there is no noble gas that precedes them
Therefore, always write long hand electron configuration