1. 4.9 – NOTES Electron Configurations

3. III. Electron Configurations
A. Ground-state electron configurations
1. The aufbau principle electrons start at the lowest level possible;

5. 2. Pauli Exclusion principle - no 2 electrons can have the same 4 quantum #s;
- even # of electrons – element can be paramagnetic or diamagnetic
- odd # of electrons – element must be paramagnetic
- if e- spin same way  should be paramagnetic (attracted by magnets); spin opposite way  diamagnetic (slightly repelled by magnet; ex – He)

7. 3. Hund’s rule - most stable arrangement of e- in subshells, one w/ greatest # of parallel spins; result electrons will NOT pair (due to repulsion) until forced to do so.

8. B. Orbital diagrams and electron configuration notations
There are 2 representations of electron configurations: orbital notation and electron configuration notation. We will start with hydrogen and work our way through the periodic table, writing both configurations.
Orbital e- configs
Hydrogen:

9. Helium:
Lithium:

10. Beryllium:
Boron:

11. Carbon:
Nitrogen:

12. Oxygen:
Fluorine:

13. Neon: