1. 1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d
7s 7p s p d f

2. √ √ EXCEPTIONS TO THE RULE 24Cr 1s2 2s2 2p6 3s2 3p6 4s2 3d4
29Cu 1s2 2s2 2p6 3s2 3p6 4s2 3d9
1s2 2s2 2p6 3s2 3p6 4s1 3d10 √ √

3. 20Ca 1s2 2s2 2p6 3s2 3p6 4s2 [ 1s2 2s2 2p6 3s2 3p6 ] 4s2 [Ar] 4s2
Shorthand method of writing the electron configuration of the elements – replace the core electrons (electrons in the inner orbitals) with the symbol of the noble gas (enclosed in square bracket) on the row above the element being considered followed by the valence (outermost shell) electron configuration
20Ca 1s2 2s2 2p6 3s2 3p6 4s2
[ 1s2 2s2 2p6 3s2 3p6 ] 4s2
[Ar] 4s2

4. VALENCE ELECTRON CONFIGURATION
arrangement of the electrons in the highest energy level.
- identified by the highest MEL and the following subshells (if any)
Example: 8O
1s2 2s2 2p4
22Ti
1s2 2s2 2p6 3s2 3p6 4s2 3d2

5. Electron Population Distribution
- Shows how the electrons are distributed among the different orbitals
- Based on the electron configuration of the elements

6. Electron Population Distribution or Electron Orbital Notation
Show the electron population distribution for 15P.
P has 15 electrons.
Its electron configuration is 1s2 2s2 2p6 3s2 3p3.
The electron population distribution for P is: 1s 2s 2p 3s 3p

7. 2s2 2p4
4s2 3d2

8. PERIODIC TABLE ACTIVITY Name __________________________________________ Period ___________________ Date ____________