1. ELECTRON CONFIGURATION The arrangement of electrons in an atom Each element has a distinct electron configuration Electron configuration describes the relationship between energy and stability

2. ELECTRON CONFIGURATION Electrons and nucleus interact to make the most stable arrangement possible (lowest energy) The lowest arrangement is the “ground-state electron configuration”

3. ELECTRON CONFIGURATION There are three rules for electron configurations Aufbau principle Pauli exclusion principle Hund’s rule

4. ELECTRON CONFIGURATION AUFBAU PRINCIPLE Electrons occupy the orbitals of lowest energy first

6. ELECTRON CONFIGURATION Aufbau order filling

7. ELECTRON CONFIGURATION Pauli exclusion principle One orbital may describe at most 2 electrons To occupy the same orbital, the two electrons must have opposite spins ↑↓

8. ELECTRON CONFIGURATION Hunds rule When filling orbitals of equal energy, One electron occupies each orbital

9. ELECTRON CONFIGURATION HUNDS RULE cont. Until all orbitals contain one electron with the same spin direction Then they can be paired ↑↑↑↑↑↑↓↑↑

10. ELECTRON CONFIGURATION Exceptions Half-filled sublevels are less stable than filled sublevels but more stable than other configurations

11. ELECTRON ARRANGEMENT Orbital notation Electron configuration notation Noble gas configuration

12. ORBITAL NOTATION Beryllium Nitrogen

13. ORBITAL NOTATION Fluorine Phosphorous

14. ELECTRON CONFIGURATION NOTATION Contains only the sublevel notation and Superscripts to indicate the number of electrons in the sublevel

15. ELECTRON CONFIGURATION NOTATION 1s 2 2s 2 2p 1 has a total of 5 electrons (2+2+1=5) In ground state = 5 protons = Atomic number 5= Boron

16. ELECTRON CONFIGURATION NOTATION 1s 2 2s 2 2p 6 = 1s 2 2s 2 2p 6 3s 1 = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 =

17. NOBLE GAS CONFIGURATION Find the noble gas (group 18) before the element you are arranging Write that noble gas configuration as [symbol] [He], [Ne], [Ar] Then continue to write the electron configuration from that point

18. NOBLE GAS CONFIGURATION Practice