1. Electron Configurations
-Each element has a unique electron configuration that determines the properties of the element.
-These configurations have influenced how the periodic table is organized

2. Electron Configurations
-The principal quantum numbers (1, 2, 3, 4, 5, 6, and 7) correspond to the periods (horizontal rows) on the periodic table.
-There are four different kinds of subshells and they only hold a certain number of electrons each.
“s” holds 2 electrons
“p” holds 6 electrons
“d” holds 10 electrons
“f” holds 14 electrons

3. Electron Configurations
The order of the subshells and quantum numbers:
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d
-Electron configurations determine how many valence electrons an element will have based on the highest level orbitals
-Patterns in valence electrons determine chemical reactivity

4. Electron Configurations
Shorthand Configuration:
[Noble Gas] __s2 __p6 etc
-Use the noble gas located periodically before the element you’re looking at and write the rest that follows
Examples: Na: [Ne] 3s1
Se: [Ar] 4s2 3d10 4p4