1. Orbital Notation, Noble Gas Notation, and Valence Electrons
Electron diagrams
Orbital Notation, Noble Gas Notation, and Valence Electrons

2. Noble Gases
Method of representing electron configurations of noble gases
Elements in the last column of the periodic table
Have 8 electrons in their outermost orbital
Extremely stable

3. Nobel Gas Notation Recall, the electron configuration for Na is:
Na: 1s2 2s2 2p6 3s1
We can abbreviate the electron configuration by indicating the innermost electrons with the symbol of the preceding noble gas.
The preceding noble gas with an atomic number less than sodium is neon, Ne. We rewrite the electron configuration:
Na: [Ne] 3s1

4. Orbital Notation
In electron configurations, we wrote the orbitals together as one sublevel
Example:
2px 2py 2pz  all became the 2p sublevel
We do not get to see how the individual electrons line up
In orbital notations, each sublevel is written to show the electron’s spins in each direction
Orbital notation shows you where each specific electron is placed (in order) and what it’s “spin” is.

5. Reference Sheet
This reference sheet shows each orbital split apart into its 3 dimensional axes

6. Electron Configuration for Na
Na, 11e-
1s2 2s2 2p6 3s1
We are now going to represent each electron as a “half arrow”
We must fill in the electrons as we did previously but show them using arrows on the orbital notation diagram
The first electron in an orbital is placed up (+1/2 spin)

7. 3px
3py
3pz 3s
2px
2py
2pz 2s 1s

8. Orbital Notation for Boron
B, 5e s2 2s2 2p1
2px
2py
2pz 2s 1s

9. Orbital Notation Practice
Helium
Boron
Carbon
Oxygen
Sodium
Manganese

10. Exceptions to Predicted Configurations
Chromium
Incorrect: [Ar] 4s23d4
Correct: [Ar] 4s13d5
Copper:
Incorrect: [Ar] 4s23d9
Correct: [Ar] 4s13d10
Elements in group 6 (s1d5) and group 11 (s1d10) have greater stability with half-filled and filled sets of s and d orbitals

11. Valence Electrons
Only certain electrons determine the chemical properties of an element
Valence Electrons:
Electrons in the atom’s outermost orbitals – generally those orbitals associated with the atom’s highest principal energy level orbitals (s and p)
Example:
Sulfur contains 16 electrons
6 electrons occupy the outermost 3s and 3p orbitals
Therefore, Sulfur has 6 valence electrons

12. Electron Dot Structures
Chemist often represent valence electrons in a short hand method
Termed Electron-Dot Structures
Structures consist of the element’s symbol surrounded by dots, representing the valence electrons