1. Understanding Electron Configuration
Essential Question: How are electrons organized for individual atoms?

2. PRINCIPAL ENERGY LEVELS
The electrons in an atom are located at specified distances from the nucleus and have different amounts of energy. Only seven (7) main --principal energy levels are necessary to account for the electrons of the known elements.
Connection to what you know: Seven periods- ---seven rings ---- Seven principal energy levels

3. Energy Sublevels and Blocks on the periodic table
Principal energy levels can be divided into sublevels. There are 4 identified sublevels: s, p, d, and f. This is how we separate the blocks on the periodic table.

4. Orbitals
Each block contains a number of columns equal to the number of electrons that can occupy that subshell
A sublevel can further be divided into orbitals, a region of space where an electron is likely to be found. Thus there are s orbitals, p orbitals, d orbitals, and f orbitals.
Each orbital can hold a maximum of 2 electrons
Sublevels
Orbitals
Electrons Possible s 1 2 p 3 6 d 5 10 f 7 14

5. What is electron configuration?
Now we can write the electron configuration notation (ECN) for any given atom
What is electron configuration?
It is also the most stable arrangement of electrons around the nucleus of an atom
Write the ECN for Oxygen (atomic # 8, therefore 8 electrons)
1s2 2s2 2p4 What does it mean?
2p4
# of Electrons in that sublevel
Principal energy level
Sublevel

6. How does it relate to what you learned?
Oxygen:
Atomic # 8
8 electrons
Its on the 2nd row so it has 2 orbitals
8p+
8n0
What you just learned:
1s s2 2p4

7. Examples
ECN for Silicon How many electrons? 14 Use the Aufbau Diagram or the location of the blocks to guide you. Fill in your electrons. You must fill an orbital in a lower energy level prior to going to the next. Don’t skip around. Look at the chart that indicates the # of electrons per orbital s = 2 e- p = 6 e- 1s2 2s2 2p6 3s2 3p2

8. Electron Configuration Notation (ECN)
Practice: Use the back of your electron configuration information sheet
Electron Configuration Notation (ECN)
1. Sulfur:
2. Potassium:
Orbital Notation (ON)
3. Sulfur
4. Potassium
Noble Gas Notation (NGN)
5. Sulfur
6. Potassium

9. Orbital Notation (ON)
Simply use lines and arrows instead of superscript numbers. Ex: Silicon
1s2 2s2 2p6 3s2 3p2
Keep in mind how many orbitals are in each of the sublevels listed. Use the chart on your info sheet.
s has one and p has three.
___ ___ ___ ___ ___ ___ ___ ___ ___
1s s p s p

10. Noble Gas Notation (NGN)
Short the configuration by using the noble gas that comes right before the element.
Example: Silicon 1s2 2s2 2p6 3s2 3p2
The noble gas that comes right before this element (silicon) is neon (element #10).
Remove the first ten electrons and replace them with the symbol for neon in brackets.
[Ne] 3s2 3p2

11. Rules to remember The Aufbau Principle
This principle simply states that we can build up an electronic configuration one electron at a time by putting each electron in the lowest energy orbital available.
The Pauli Exclusion Principle
This principle says that an orbital is filled when it contains 2 electrons. After that, you have to put the electrons in a different orbital.
Hund's Rule
Within a subshell, the electrons will occupy the orbitals singly first, and will only pair up when there are no longer any empty orbitals available in that subshell.