1. Orbitals each sublevel is broken into orbitals
each orbital can hold a maximum of 2 electrons
orbital- a 3D region around the nucleus that has a high probability of holding electrons

2. Number of Orbitals sublevel max # e- # orbitals s 2 1 p 6 3 d 10 5

3. One s orbital
spherical

4. Three p orbitals
dumbbell-shaped

5. Five d orbitals
various shapes

6. Seven f orbitals
various shapes

7. Energy Number of Types of
Level Sublevels Sublevels s
s,p
s,p,d
s,p,d,f

8. Energy Level
Sublevels #
Orbitals
Total Orbitals
Total Electrons 1 2 3 4

9. Energy Level
Sublevels #
Orbitals
Total Orbitals
Total Electrons 1 s 2 4 8 p 3 9 18 d 5 16 32 f 7

10. Electron Configurations
the arrangement of electrons in an atom
each type of atom has a unique electron configuration
electrons tend to assume positions that create the lowest possible energy for atom
ground state electron configuration- lowest energy arrangement of electrons

11. Rules for Arrangements
Aufbau Principle- an electron occupies the lowest-energy orbital that can receive it
Beginning in the 3rd energy level, the energies of the sublevels in different energy levels begin to overlap

12. Rules for Arrangements
Pauli Exclusion Principle- no more than two electrons can occupy an orbital at a time, and they must have opposite spins.

13. Rules for Arrangements
Hund’s Rule- orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second (fill empty orbitals with 1 before pairing)

14. Rules for Arrangements
all unpaired electrons must have the same spin

15. Rules for Arrangements

16. Writing Configurations
Orbital Notation:
an orbital is written as a line
each orbital has a name written below it
electrons are drawn as arrows (up and down)
Electron Configuration Notation
number of electrons in sublevel is added as a superscript

17. Order for Filling Sublevels

18. Writing Configurations
Start by finding the number of electrons in the atom
Identify the sublevel that the last electron added is in by looking at the location in periodic table
Draw out lines for each orbital beginning with 1s and ending with the sublevel identified
Add arrows individually to the orbitals until all electrons have been drawn

19. Silicon number of electrons: 14 last electron is in sublevel: 3p
1s 2s p s p
Valence Electrons- the electrons in the outermost energy level

20. Chlorine number of electrons: 17 last electron is in sublevel: 3p
1s 2s
2p s p

21. Sodium number of electrons: 11 last electron is in sublevel: 3s
1s2 2s2 2p6 3s1
1s s p 3s

22. Calcium number of electrons: 20 last electron is in sublevel: 4s
1s2 2s2 2p6 3s2 3p6 4s2
1s s p 3s
3p 4s

23. Bromine number of electrons: 35 last electron is in sublevel: 4p
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
1s s p 3s 3p
1s s p 3s 3p
4s 3d p
4s 3d p

24. Argon number of electrons: 18 last electron is in sublevel: 3p
1s2 2s2 2p6 3s2 3p6
1s s p 3s 3p

25. Noble Gas Notation short hand for larger atoms
configuration for the last noble gas is abbreviated by the noble gas’s symbol in brackets